/dev/ragfield

Power Smart Pricing

2010-05-26T16:19:00.001-05:00

Ameren Illinois Utilities Power Smart Pricing data is available in tabular form on the web. This function will scrape that data and return the rate in US dollars for a given date/time. My friend John wanted to use this data for something I didn't quite understand...

Date[]

{2010, 5, 26, 16, 3, 34.163065`8.286131807151374}

PowerSmartPrice[{y_, m_, d_, h_, mm_, s_}]:=Module[
    {url, data},
    url = StringJoin["http://www.powersmartpricing.org/chart/?display=table&price_dt=", ToString[m], "/", ToString[d], "/", ToString[y]];
    data = Import[url, "Data"][[2;;]];
    ToExpression[StringDrop[data[[Floor[h] + 1, 2]], - 1]] / 100.
];

PowerSmartPrice[Date[]]

0.065`

PowerSmartPrice[{2010, 5, 25, 16, 0, 0}]

0.066`

Play a specific track in iTunes from Mathematica

2009-10-21T07:47:00.001-05:00

A coworker was making a presentation and asked me for a function he could trigger with Button[] to start playing a specific track in iTunes (on a Mac). This gets the job done:

iTunesPlay[playlist_String, track_Integer] := Run[StringJoin[
"osascript -e 'tell application \"iTunes\" to play track ",
ToString[track], " of user playlist \"", playlist, "\"'"
]];

iTunesPlay["Mix", 1]

iTunesPlay["Mix", 2]

Use BBEdit for diffing with Mercurial

2009-10-08T17:17:00.001-05:00

Add the following lines to your ~/.hgrc file:

[extensions]
hgext.extdiff =

[extdiff]
cmd.bbdiff = bbdiff
opts.bbdiff = --resume --wait --reverse

Then diff with the bbdiff command:

$ hg bbdiff [...]

Insert text at the current cursor location in a UITextField on iPhone OS 3.0

2009-09-15T08:58:00.001-05:00

The text widgets (UITextField, UITextView, etc) in the iPhone OS SDK appear to have been intentionally designed to allow as little control for 3rd party developers as possible. I found myself needing a user interface in an iPhone application which has buttons (in addition to the standard keyboard) that insert text into the currently selected UITextField. Neither UITextField nor any of it's parent classes or protocols have such a method.

One possible solution would be to get the contents of the UITextField, append the desired text to it, then set the contents of the UITextField to the new string. This gives the expected behavior if the text cursor is at the end of the text (which it usually is), but it does not give the correct behavior when the text cursor is anywhere else within the text.

There is a solution in iPhone OS 3.0. The method -(void)paste:(id)sender inserts the text from the system pasteboard at the current text cursor location. So all we need to do is temporarily hijack the system pasteboard. The basic steps are as follows:

get a reference to the system pasteboard
save the contents of the pasteboard so you can restore them later
change the contents of the pasteboard to include the text you wish to insert
send the -(void)paste:(id)sender message to the responder (UITextField or UITextView)
restore the contents of the system pasteboard

Here is a simple category on UIResponder which adds a -(void)insertText:(NSString*)text method to this base class that should work on any text editing view.

@interface UIResponder(UIResponderInsertTextAdditions)
- (void) insertText: (NSString*) text;
@end

@implementation UIResponder(UIResponderInsertTextAdditions)

- (void) insertText: (NSString*) text
{
	// Get a refererence to the system pasteboard because that's
	// the only one @selector(paste:) will use.
	UIPasteboard* generalPasteboard = [UIPasteboard generalPasteboard];
	
	// Save a copy of the system pasteboard's items
	// so we can restore them later.
	NSArray* items = [generalPasteboard.items copy];
	
	// Set the contents of the system pasteboard
	// to the text we wish to insert.
	generalPasteboard.string = text;
	
	// Tell this responder to paste the contents of the
	// system pasteboard at the current cursor location.
	[self paste: self];
	
	// Restore the system pasteboard to its original items.
	generalPasteboard.items = items;
	
	// Free the items array we copied earlier.
	[items release];
}

@end

Upload videos to YouTube with Mathematica

2009-07-08T08:32:00.001-05:00

First, install the GData package in $UserBaseDirectory/Applications. Load the GData package which contains the code used to interact with YouTube (and other Google services).

<<GData`

Next, log in to YouTube. This will prompt for a user name and/or password if either is not specified.

yt = YouTubeLogin["User"->"robragfield"]

YouTube[<...>]

We can make sure it's working by asking for a list of videos uploaded to this account.

("Title"/.#)&/@YouTubeUploads[yt]

{OmetepeProfile.mov, Homer Fireworks, Tripod, Cobb Park Crit, Mt. Diablo descent, Seymour TT starts, Screaming hard drive, Descent (iMovie image stabilization comparison), Descent, Descent, Carpenter Park Cross #2 (Line Art), Indy Marathon chase}

We can also check out other accounts.

YouTubeUploads[yt, "wolframmathematica"]//Length

950

Finally, we can upload a new video to YouTube.

YouTubeUpload[yt, "/Users/schofield/Movies/carpenter_park_2.mp4", "Title"->"Carpenter", "Description"->"Carpenter Park cyclocross race"]

«JavaObject[com.google.gdata.data.youtube.VideoEntry]»

You can also specify the category and keywords.

Options[YouTubeUpload]

{Title->Automatic, Description->Undescripted, Category->Tech, Keywords->{uploaded by Mathematica}}

Download Mathematica notebook.

Download GData package.

I thought 802.11N 5GHz was the fastest

2009-07-03T22:55:00.001-05:00

Not so. While I was setting up my Airport Extreme 802.11N (gigabit ethernet) router I could have sworn I read that the fastest wireless performance would be achieved with 802.11N-Only 5GHz mode, so this is what I have been using for the past year+. All our computers and the AppleTV use 802.11N, but our iPhones only have 802.11G. So I set up my old Airport Extreme 802.11G (hershey kiss) router to handle the iPhones.

Anyway, this causes some annoying problems where apparently iPhone & desktop apps which are supposed to sync with each other don't work very well (Apple's Remote and Filemaker's Bento come to mind). Even though they're on the same subnet the syncing was just incredibly unreliable. It would work every once in a while, but usually it would just wait forever for a connection that never came.

A little frustrated with the situation I decided to try out some of the other modes for the Airport Extreme 802.11N router to see how much worse the network performance was. Perhaps I'd be willing to live with a slight performance hit if it meant more reliable iPhone app syncing.

I was shocked to find that, of all the available modes, the supposed fastest mode I had been using all this time was actually the slowest. I saw roughly twice the file transfer speed using 2.4 GHz, even when G/B compatible mode was enabled, even when the 802.11G iPhone was connected to the router loading web pages.

For each of the modes I copied a 246 MB file using scp from my MacBook Pro 15" downstairs to my Mac Pro desktop upstairs. Twice.

schofieldmaclap.local (802.11N/5.0GHz) Airport Extreme (gigabit) macpro.local

[schofieldmaclap:tmp]$ scp ApertureTrial.dmg macpro.local:/tmp/
ApertureTrial.dmg                             100%  246MB   3.7MB/s   01:07    
[schofieldmaclap:tmp]$ scp ApertureTrial.dmg macpro.local:/tmp/
ApertureTrial.dmg                             100%  246MB   3.7MB/s   01:06    


schofieldmaclap.local (802.11N/G/B/2.4GHz) Airport Extreme (gigabit) macpro.local

[schofieldmaclap:tmp]$ scp ApertureTrial.dmg macpro.local:/tmp/
ApertureTrial.dmg                             100%  246MB   7.9MB/s   00:31    
[schofieldmaclap:tmp]$ scp ApertureTrial.dmg macpro.local:/tmp/
ApertureTrial.dmg                             100%  246MB   8.2MB/s   00:30    


schofieldmaclap.local (802.11N/G/B/2.4GHz/iPhone) Airport Extreme (gigabit) macpro.local

[schofieldmaclap:tmp]$ scp ApertureTrial.dmg macpro.local:/tmp/
ApertureTrial.dmg                             100%  246MB   7.9MB/s   00:31    
[schofieldmaclap:tmp]$ scp ApertureTrial.dmg macpro.local:/tmp/
ApertureTrial.dmg                             100%  246MB   8.2MB/s   00:30    


schofieldmaclap.local (802.11N/2.4GHz) Airport Extreme (gigabit) macpro.local

[schofieldmaclap:tmp]$ scp ApertureTrial.dmg macpro.local:/tmp/
ApertureTrial.dmg                             100%  246MB   7.5MB/s   00:33    
[schofieldmaclap:tmp]$ scp ApertureTrial.dmg macpro.local:/tmp/
ApertureTrial.dmg                             100%  246MB   8.5MB/s   00:29    


schofieldmaclap.local (802.11N/5.0GHz) Airport Extreme (gigabit) macpro.local

[schofieldmaclap:tmp]$ scp ApertureTrial.dmg macpro.local:/tmp/
ApertureTrial.dmg                             100%  246MB   3.5MB/s   01:11    
[schofieldmaclap:tmp]$ scp ApertureTrial.dmg macpro.local:/tmp/
ApertureTrial.dmg                             100%  246MB   3.5MB/s   01:11

I guess I'll be switching to 802.11N/G/B compatible mode.

Link: Creating and Post-Processing Mathematica Graphics on Mac OS X

2009-06-18T11:28:00.001-05:00

Creating and Post-Processing Mathematica Graphics on Mac OS X

This user does a good (and thorough) job at enumerating a number of potential problems one could run into when creating and exporting graphics in Mathematica. In most cases the user also includes workarounds. In some cases the user's assumptions/explanations aren't technically correct, but the workarounds are still well thought out.

Twitter usage patterns

2009-05-21T23:15:00.001-05:00

What kind of Twitterer am I? I'm kind of on a role with this data mining of Twitter so I'll take a brief look at my own Twitter habits.

<<Twitter`

session = TwitterSessionOpen["User"->"ragfield"]

TwitterSession[<ragfield>]

Length[tweets = TwitterUserAllTimeline[session]]

1487

DateDifference[TwitterStatusDate@Last@tweets, TwitterStatusDate@First@tweets, {"Year", "Month", "Day"}]

{{1, Year}, {3, Month}, {20.83855324074074`, Day}}

Length[tweets] / DateDifference[TwitterStatusDate@Last@tweets, TwitterStatusDate@First@tweets, {"Day"}][[1, 1]]

3.125009501379522`

1487 total tweets in the last 1 year, 3 months, and 21 days. On average that's 3.125 tweets per day.

DateListPlot[Tally[{#[[1]], #[[2]], 1, 0, 0, 0.}&/@(TwitterStatusDate/@tweets)], Joined->True, Filling->Axis, FrameLabel->{"Month", "Tweets per month"}, PlotLabel->"Ragfield Twitter usage", DateTicksFormat->{"MonthNameShort", " ", "Year"}]

Total[StringLength[TwitterStatusText[#]]&/@tweets]

107442

N[% / Length[tweets]]

72.2542030934768`

107,442 total characters typed. On average that's 72 characters per tweet, roughly half the allotted space.

First@SortBy[TwitterStatusText/@tweets, StringLength]

bed

My shortest tweet was simply "bed".

Length[allWords = StringSplit[StringJoin[Riffle[TwitterStatusText/@tweets, " "]], Except[WordCharacter|"'"]..]]

19188

19,188 unique words typed.

Length[allWords = DeleteCases[allWords, x_/;StringMatchQ[x, DigitCharacter..]]]

18528

18,528 if you don't count numbers.

First@Reverse@SortBy[Tally[allWords], Part[#, 2]&]

{the, 604}

The most common word I've typed is "the". That's not terribly useful. Let's take a look at just nouns to see what kind of topics I mention most frequently.

Length[nouns = Cases[allWords, x_/;MemberQ[WordData[x], "Noun", ‚àû]]]

7883

Grid[Take[Reverse@SortBy[Tally[nouns], Part[#, 2]&], 30], Alignment->{{Right, Left}}]

I	431
a	419
in	259
at	126
have	77
bike	62
work	54
time	52
out	51
are	48
ride	45
think	43
so	43
run	43
now	42
like	42
one	38
d	38
morning	36
last	36
can	36
race	35
miles	35
mile	35
home	35
first	35
way	34
still	34
year	31
good	31

Most common topics: bike, work, time, ride, think, run, like, morning, race, mile(s), home.

We can do the same thing with verbs to see what kind of actions I describe most frequently.

Length[verbs = Cases[allWords, x_/;MemberQ[WordData[x], "Verb", ‚àû]]]

4300

Grid[Take[Reverse@SortBy[Tally[verbs], Part[#, 2]&], 30], Alignment->{{Right, Left}}]

is	164
was	108
be	80
have	77
bike	62
up	59
work	54
time	52
out	51
ride	45
been	44
think	43
run	43
has	43
like	42
last	36
can	36
race	35
home	35
still	34
had	32
got	32
get	30
do	30
back	28
long	27
will	26
see	26
did	25
know	24

Most common actions: bike, work, ride, think, run, race, see, know. I guess there's a lot of overlap between the nouns and the verbs.

It's also pretty easy to determine the other users I mention most frequently.

Grid[Take[Reverse@SortBy[Tally[StringCases[StringJoin[Riffle[TwitterStatusText/@tweets, " "]], "@"~~a:Except[WhitespaceCharacter]..:>Hyperlink[ToLowerCase[a], "http://twitter.com/"<>ToLowerCase[a]]]], Part[#, 2]&], 10]]

melissa_raguet	84
spoonshake	69
esmithrunner	32
erik_d	28
dbfulton	18
gutzville	14
ultrashea	11
erik__d	9
adamengst	9
chockenberry	6

Downloads

Download Twitter.m.

Download WebUtils.m (required by Twitter.m).

Download Mathematica Notebook.

Wolfram|Alpha tweet analysis

2009-05-20T23:54:00.001-05:00

Last month I wrote about my Twitter package for Mathematica. Shortly thereafter I wrote a similar post for my company's blog. That post seems to have been well received and has generated quite a bit of interest on Twitter.

I have continued to add useful features to the package, including the ability to search Twitter.

<<Twitter`

Column[Take[TwitterSearch["twitter mathematica"], 5], Dividers->All]

TwitterStatus[<netzturbine: ‚ô∫ @imabug cool, mathematica + the twitter API http://bit.ly/1Wv0iV - should work w/ !laconica 2>]

TwitterStatus[<imabug: cool, mathematica and the twitter API http://bit.ly/1Wv0iV>]

TwitterStatus[<kdrewien: RT @PragueBob Wolframs mainstream Mathematica software is plugging into Twitter: http://cli.gs/257htM Geeky!>]

TwitterStatus[<lunajade: How to Twitter with Mathematica and analyze the data... http://bit.ly/14WA8F (via @WolframResearch) [VERY interesting...]>]

TwitterStatus[<pythonism: http://twitter.com/MikeCr/statuses/1835493378 "@ruby_gem Mathematica, firefox, python">]

Adding this functionality was actually a little more difficult than it should have been because the Twitter search API returns a different flavor of XML (ATOM) than the regular Twitter API.

Also, I renamed the HTTP.m package (which was used by Twitter.m) to WebUtils.m and I added some other useful functionality, including the ability to interact with a few popular URL shortening/expanding services. This has enabled some interesting possibilities.

Tweet cache

As you may already know, Wolfram|Alpha launched this past weekend. The website went live on Friday evening and the official launch was Monday afternoon. Sometime Friday afternoon I started running a short Mathematica program that used the TwitterSearch[] function to download all tweets mentioning Wolfram|Alpha and stuff them into an SQLite database. The program is still running, downloading new tweets as they happen.

db = Database`OpenDatabase["Twitter.sqlite"]

Database`Database[Twitter.sqlite]

Database`QueryDatabase[db, "CREATE TABLE tweets (id INTEGER PRIMARY KEY, text TEXT, source TEXT, created_at DATE, in_reply_to_status_id INTEGER, in_reply_to_user_id INTEGER, in_reply_to_screen_name TEXT, user_id INTEGER, user_screen_name TEXT, user_name TEXT, user_profile_image_url TEXT);"];

TwitterStatusDateDBString[status_TwitterStatus] :=
    DateString[TwitterStatusDate[status], {
            "Year", "-", "Month", "-", "Day", " ",
            "Hour", ":", "Minute", ":", "Second"
        }];

InsertTweet[db_Database`Database, status_TwitterStatus]:=Module[{query, user, vals}, query = "INSERT INTO tweets (id, text, source, created_at, in_reply_to_status_id, in_reply_to_user_id, user_screen_name, user_name, user_profile_image_url) values (?, ?, ?, ?, ?, ?, ?, ?, ?)";
    user = TwitterStatusUser[status];
    vals = {
        TwitterStatusID[status],
        TwitterStatusText[status],
        TwitterStatusSource[status],
        TwitterStatusDateDBString[status],
        TwitterStatusReplyID[status],
        TwitterStatusReplyUserID[status],
        TwitterUserScreenName[user],
        TwitterUserName[user],
        TwitterUserProfileImageURL[user]
    };
    Database`QueryDatabase[db, query, vals]
];

query = "wolframalpha OR wolfram_alpha OR \"wolfram alpha\"";

TwitterSearchSince[query_String, id_Integer]:=Module[{tweets = {}, lastCount = - 1, page = 1},
    While[Length[tweets] =!= lastCount,
        lastCount = Length[tweets];
        tweets = Join[tweets,
            TwitterSearch[query, "Results"->100, "Since"->id, "Page"->page++]
        ]
    ];
    tweets
];

since = TwitterStatusID[First[TwitterSearch[query]]];

UpdateCache[]:=While[True,
    tweets = TwitterSearchSince[query, since];
    Monitor[
        Do[InsertTweet[db, tweets[[i]]], {i, Length[tweets]}], ProgressIndicator[Dynamic[i/Length[tweets]]]
    ];
    since = If[Length[tweets]>0, TwitterStatusID[First[tweets]], since];
    Print["added ", ToString[Length[tweets]], " tweets to database at ", DateString[]];
    Pause[30]
];

UpdateCache[]

I chose SQLite because it's easy to use, it's included with Mathematica (though possibly undocumented), it can be accessed easily via a command line tool, and it can be safely accessed by multiple processes at the same time. I started the program five days ago and it's still running. I am able to query the database from a different Mathematica process without interrupting the tweet downloads.

Tweet rate

So, from the other instance of Mathematica I am able to do things like this.

db = Database`OpenDatabase["Twitter.sqlite"]

Database`Database[Twitter.sqlite]

Length[ids = Database`QueryDatabase[db, "select id from tweets"]]

62659

62,659 tweets mentioning Wolfram|Alpha between Friday and Wednesday of launch week. Let's take a look at the timeline. First, grab the creation date of each tweet in the database.

dateStrs = Database`QueryDatabase[db, "select created_at from tweets"];

Convert the strings into Mathematica DateList[] notation.

dates = Monitor[Table[DateList[dateStrs[[i, 1]]], {i, Length[dateStrs]}], ProgressIndicator[Dynamic[i / Length[dateStrs]]]];

Tally the number of tweets per hour.

tally = Tally[{#[[1]], #[[2]], #[[3]], #[[4]], 0, 0}&/@dates];

DateListPlot[tally, Joined->True, FrameLabel->{"Date", "Tweets per hour"}, PlotRange->{{First[dates], DatePlus[DateList[], { - 1, "Hour"}]}, Automatic}, PlotLabel->"Wolfram|Alpha tweet rate", Filling->Axis, ImageSize->{500, Automatic}]

There are large spikes in tweets per hour around the time the website went live on Friday evening, and again when the site officially launched on Monday.

Tweet links

Since many people post URLs in their tweets it might be interesting to take a look at these to see which web pages and blogs about Wolfram|Alpha are generating the most interest.

tweets = Database`QueryDatabase[db, "select text from tweets"][[All, 1]];

There is a wide variation in the way people post URLs to Twitter, so unfortunately I couldn't find a single regular expression that would find every single one of them. This one works reasonably well.

Length[urls = Flatten[StringCases[#, "http://"~~Except[">"|"]"|"\""|"'"|","|WhitespaceCharacter]..]&/@tweets]]

37565

Length[tally = Tally[urls]]

17969

So there appear to be 37,565 links posted, 17,969 of which are unique. The thing about these URLs is that many use URL shortening services. So it's quite possible many shortened URLs point to the same destination URL. No matter. We can use the URLExpand[] function in my WebUtils package to expand URLs from many of the common URL shortening services.

Unfortunately, that much network traffic takes a long time. So let's cache the results as a list of rules so we can avoid future lookups of the same short URL if possible.

urlMap = {};

expandURL[url_String] := Module[
    {newurl},
    newurl = url /. urlMap;
    If[newurl === url,
        newurl = URLExpand[url];
        If[newurl =!= url, AppendTo[urlMap, url->newurl]];
    ];
    newurl
];

This expansion takes quite some time.

expanded = Monitor[Table[expandURL[urls[[i]]], {i, Length[urls]}], ProgressIndicator[Dynamic[i / Length[urls]]]];

Length[tally = Reverse@SortBy[Tally[expanded], Part[#, 2]&]]

14609

Let's take a look at all of the expanded URLs which were posted more than 100 times.

BarChart[Labeled[Hyperlink[#[[2]], #[[1]]], Rotate[#[[1]], Pi / 2], {Bottom}]&/@Cases[tally, {url_String, n_Integer}/;n>100], ImageSize->{500, Automatic}]

Grid[{#[[2]], Hyperlink[#[[1]]]}&/@Take[tally, 30], Dividers->All, Alignment->{{Right, Left}}]

4475	http://www.wolframalpha.com/
1443	http://www.wolframalpha.com/screencast/introducingwolframalpha.html
1428	http://www.wolframalpha.com
1004	http://mashable.com/2009/05/17/wolfram-easter-eggs/
590	http://mashable.com/2009/05/19/wolfram-alpha-better-than-google/
528	http://mashable.com/2009/05/17/better-wolfram-easter-eggs/
331	http://nakedoncam.info/free
316	http://www.wolframalpha.com/input/
316	http://www.wolframalpha.com/index.html
312	http://wolframalpha.com
291	http://www.justin.tv/wolframalpha
276	http://www.wolfram.com/broadcast/wolframalpha/
201	http://justin.tv/wolframalpha
188	http://mashable.com/2009/05/15/wolfram-alpha-launch-2/
184	http://mashable.com/2009/05/15/wolfram-alpha-video/
173	http://www.youtube.com/watch?v=ASnHvwmHuMQ
172	http://www.justin.tv/clip/2dd6b9f07e7f8a4e
126	http://www.you-got-rick-rolled.com
100	http://you-got-rick-rolled.com
97	http://www.theregister.co.uk/2009/05/19/dziuba_wolfram/
89	http://www.hothotjoboffers.com/32/
87	http://business.timesonline.co.uk/tol/business/industry_sectors/technology/article6307744.ece
81	http://wolframalpha.com/
72	http://www.wolframalpha.com.
71	http://lifehacker.com/5257400/first-look-at-wolfram-alphas-impressive-and-fun-knowledge-computation
69	http://www.wolframalpha.com/examples/
69	http://tedchris.posterous.com/wolfram-alpha-vs-google-1
69	http://news.google.com/news/url?sa=T&amp
65	http://www.readwriteweb.com/archives/wolfram_alpha_launch_starts_tonight.php
61	http://www.wolframalpha.com/input/?i=meaning+of+life

So we have a whole bunch of links directly to the Wolfram|Alpha website, a bunch links to the screencast, a lot of links to some Easter eggs, a porn site (hmmm...), the justin.tv broadcast, Rick-Roll URLs, blog posts, etc. Interesting stuff.

Downloads

Download Twitter.m.

Download WebUtils.m (required by Twitter.m).

Download Mathematica Notebook.

Tri the Illini swim analysis

2009-05-05T11:59:00.001-05:00

On Saturday I participated in the Tri the Illini triathlon on the University of Illinois campus. You can read all about the race here. One of the interesting things about this race is that participants were started 10 seconds apart in order of their estimated time for the 300 meter swim in the indoor pool. In theory, if everyone swims at their estimated time nobody will have to pass anyone else in the pool. Now that the results have been posted, let's take a quick look to see how accurate the participants' predictions were.

Import the data from the results web page.

data = Import["http://www.mattoonmultisport.com/images/stories/results/trithetri/overall.htm", {"HTML", "FullData"}];

Clean it up a bit by removing empty elements, labels, and column headers. Basically, we only want the entries with an integer value in the first column (the overall place).

Length[data]

data = DeleteCases[data, {}|{{}}];

Length[data]

data = First[data];

Length[data]

345

Take[data, 12]//InputForm

{{"", "------- Swim -------", "------- T1 -------",
"------- Bike -------", "------- T2 -------", "------- Run -------",
"Total"}, {"Place", "Name", "Bib No", "Age", "Rnk", "Time", "Pace",
"Rnk", "Time", "Pace", "Rnk", "Time", "Rate", "Rnk", "Time", "Pace",
"Rnk", "Time", "Pace", "Time"}, {1, "Daniel Bretscher", 8, 26, 3,
"04:19.75", "23:59/M", 1, "00:34.00", "", 1, "26:42.95", "24.7mph",
19, "00:44.25", "", 2, "16:09.15", "5:23/M", "48:30.10"},
{2, "Michael Bridenbaug", 27, 25, 15, "04:39.50", "25:50/M", 6,
"00:43.65", "", 5, "28:16.55", "23.3mph", 6, "00:37.55", "", 4,
"16:15.75", "5:25/M", "50:33.00"}, {3, "Peter Garde", 17, 24, 24,
"04:53.05", "27:08/M", 51, "01:21.90", "", 2, "27:06.50", "24.4mph",
109, "01:05.95", "", 3, "16:13.05", "5:24/M", "50:40.45"},
{4, "Nickolaus Early", 16, 29, 2, "04:07.30", "22:52/M", 18,
"00:57.45", "", 4, "27:58.40", "23.6mph", 4, "00:36.40", "", 9,
"18:01.25", "6:00/M", "51:40.80"}, {5, "Zach Rosenbarger", 78, 33, 50,
"05:15.85", "29:10/M", 45, "01:16.75", "", 3, "27:42.00", "23.8mph",
54, "00:53.30", "", 5, "17:11.80", "5:44/M", "52:19.70"},
{6, "Edward Elliot", 32, 28, 11, "04:35.45", "25:28/M", 16, "00:56.15",
"", 6, "28:23.40", "23.3mph", 38, "00:48.85", "", 7, "17:43.75",
"5:54/M", "52:27.60"}, {7, "Ryan Forster", 28, 27, 35, "05:03.95",
"28:03/M", 9, "00:46.20", "", 12, "29:39.95", "22.3mph", 39,
"00:49.05", "", 11, "18:07.00", "6:02/M", "54:26.15"},
{8, "Jun Yamaguchi", 15, 27, 27, "04:58.20", "27:36/M", 2, "00:37.85",
"", 11, "29:36.70", "22.3mph", 30, "00:47.05", "", 13, "18:49.30",
"6:16/M", "54:49.10"}, {9, "Scott Paluska", 63, 42, 71, "05:35.30",
"31:01/M", 3, "00:40.70", "", 7, "28:44.00", "23.0mph", 118,
"01:06.90", "", 12, "18:43.60", "6:14/M", "54:50.50"},
{10, "Rob Raguet-Schoofield", 42, 31, 44, "05:09.75", "28:37/M", 20,
"01:01.55", "", 18, "30:10.50", "21.9mph", 45, "00:51.45", "", 8,
"17:52.60", "5:57/M", "55:05.85"}}

data = DeleteCases[data, x_/;Head[First[x]] === String];

Length[data]

301

places = data[[All, 1]];

places==Range[301]

True

swimSeeds = data[[All, 3]];

swimPlaces = data[[All, 5]];

swimΔ = swimPlaces - swimSeeds;

Take a look at {overall place, swim seed, swim place, swim Δ} for each participant. A negative Δ means the participant's swim place was better than their seeded swim place, while a positive Δ means the participant's swim place was worse than their seeded swim place.

Grid[Prepend[Transpose[{places, swimSeeds, swimPlaces, swimΔ}], {"Overall\nPlace", "Swim\nSeed", "Swim\nPlace", "Swim\nΔ"}], Dividers->All]

Overall Place	Swim Seed	Swim Place	Swim Δ
1	8	3	- 5
2	27	15	- 12
3	17	24	7
4	16	2	- 14
5	78	50	- 28
6	32	11	- 21
7	28	35	7
8	15	27	12
9	63	71	8
10	42	44	2
11	9	9	0
12	62	31	- 31
13	54	105	51
14	30	14	- 16
15	200	155	- 45
16	14	8	- 6
17	83	83	0
18	6	33	27
19	47	53	6
20	66	34	- 32
21	40	102	62
22	86	106	20
23	100	75	- 25
24	45	59	14
25	120	58	- 62
26	4	12	8
27	3	36	33
28	33	13	- 20
29	51	25	- 26
30	72	115	43
31	12	16	4
32	39	7	- 32
33	65	66	1
34	330	240	- 90
35	48	64	16
36	21	6	- 15
37	13	5	- 8
38	68	56	- 12
39	212	89	- 123
40	214	79	- 135
41	67	45	- 22
42	76	21	- 55
43	75	211	136
44	81	63	- 18
45	251	172	- 79
46	44	114	70
47	162	95	- 67
48	7	4	- 3
49	74	92	18
50	55	48	- 7
51	52	29	- 23
52	237	124	- 113
53	11	18	7
54	77	98	21
55	56	30	- 26
56	117	104	- 13
57	1	1	0
58	300	74	- 226
59	151	125	- 26
60	139	82	- 57
61	274	151	- 123
62	64	22	- 42
63	122	87	- 35
64	36	37	1
65	250	243	- 7
66	154	148	- 6
67	121	90	- 31
68	136	258	122
69	282	146	- 136
70	87	69	- 18
71	112	110	- 2
72	315	278	- 37
73	24	19	- 5
74	80	77	- 3
75	135	184	49
76	69	97	28
77	185	163	- 22
78	59	49	- 10
79	128	94	- 34
80	60	51	- 9
81	187	28	- 159
82	35	20	- 15
83	113	134	21
84	90	40	- 50
85	163	17	- 146
86	22	38	16
87	133	200	67
88	267	73	- 194
89	256	145	- 111
90	92	122	30
91	159	206	47
92	165	130	- 35
93	137	153	16
94	149	128	- 21
95	104	80	- 24
96	182	136	- 46
97	26	46	20
98	172	93	- 79
99	241	55	- 186
100	277	109	- 168
101	114	165	51
102	97	103	6
103	131	159	28
104	228	194	- 34
105	46	117	71
106	141	199	58
107	132	162	30
108	246	132	- 114
109	115	205	90
110	213	183	- 30
111	127	181	54
112	157	147	- 10
113	254	131	- 123
114	266	256	- 10
115	41	61	20
116	61	39	- 22
117	43	41	- 2
118	191	196	5
119	106	257	151
120	96	81	- 15
121	234	60	- 174
122	201	85	- 116
123	108	142	34
124	161	218	57
125	123	149	26
126	98	150	52
127	138	271	133
128	265	179	- 86
129	195	54	- 141
130	50	86	36
131	53	161	108
132	170	137	- 33
133	58	26	- 32
134	169	120	- 49
135	204	249	45
136	342	65	- 277
137	91	100	9
138	103	47	- 56
139	125	182	57
140	82	68	- 14
141	88	76	- 12
142	147	241	94
143	238	107	- 131
144	303	202	- 101
145	70	191	121
146	297	247	- 50
147	188	178	- 10
148	2	10	8
149	130	164	34
150	311	288	- 23
151	168	187	19
152	283	158	- 125
153	144	216	72
154	295	287	- 8
155	208	244	36
156	287	157	- 130
157	111	176	65
158	199	111	- 88
159	272	223	- 49
160	179	242	63
161	84	190	106
162	310	152	- 158
163	109	118	9
164	37	67	30
165	180	227	47
166	340	135	- 205
167	328	193	- 135
168	263	197	- 66
169	312	250	- 62
170	148	143	- 5
171	242	224	- 18
172	278	230	- 48
173	253	139	- 114
174	292	279	- 13
175	10	32	22
176	276	254	- 22
177	18	101	83
178	155	167	12
179	271	276	5
180	102	169	67
181	192	248	56
182	257	78	- 179
183	93	210	117
184	346	294	- 52
185	255	269	14
186	158	192	34
187	49	171	122
188	126	201	75
189	143	140	- 3
190	231	88	- 143
191	220	186	- 34
192	298	177	- 121
193	107	144	37
194	94	129	35
195	129	188	59
196	184	274	90
197	116	273	157
198	224	259	35
199	186	214	28
200	174	198	24
201	290	221	- 69
202	95	175	80
203	152	215	63
204	189	246	57
205	156	239	83
206	336	141	- 195
207	118	174	56
208	197	91	- 106
209	194	280	86
210	196	212	16
211	291	121	- 170
212	190	189	- 1
213	247	119	- 128
214	286	126	- 160
215	219	52	- 167
216	229	170	- 59
217	23	23	0
218	236	277	41
219	235	265	30
220	252	204	- 48
221	258	281	23
222	99	84	- 15
223	211	226	15
224	279	272	- 7
225	216	267	51
226	167	116	- 51
227	243	275	32
228	262	220	- 42
229	230	154	- 76
230	288	166	- 122
231	337	251	- 86
232	269	228	- 41
233	233	252	19
234	20	208	188
235	110	185	75
236	308	284	- 24
237	261	231	- 30
238	245	127	- 118
239	343	283	- 60
240	160	70	- 90
241	150	264	114
242	85	156	71
243	5	173	168
244	347	213	- 134
245	153	203	50
246	175	219	44
247	339	298	- 41
248	134	290	156
249	203	42	- 161
250	348	282	- 66
251	289	112	- 177
252	124	168	44
253	218	238	20
254	145	207	62
255	119	113	- 6
256	183	123	- 60
257	299	236	- 63
258	73	62	- 11
259	302	261	- 41
260	29	96	67
261	57	57	0
262	173	225	52
263	281	255	- 26
264	31	99	68
265	275	270	- 5
266	319	296	- 23
267	181	245	64
268	178	301	123
269	89	108	19
270	307	291	- 16
271	294	229	- 65
272	215	43	- 172
273	176	160	- 16
274	270	180	- 90
275	240	195	- 45
276	217	263	46
277	318	302	- 16
278	316	303	- 13
279	285	237	- 48
280	280	297	17
281	177	72	- 105
282	207	234	27
283	314	217	- 97
284	309	232	- 77
285	306	253	- 53
286	248	292	44
287	193	289	96
288	296	286	- 10
289	227	285	58
290	171	222	51
291	345	304	- 41
292	305	262	- 43
293	71	268	197
294	264	266	2
295	226	235	9
296	225	209	- 16
297	273	295	22
298	244	260	16
299	142	305	163
300	209	306	97
301	313	307	- 6

It looks like the race leaders were fairly accurate in their predictions, while the differences start to become greater around 40th place or so.

BarChart[swimΔ, FrameLabel->{"Overall Place", "Swim Δ"}, Frame->{True, True, False, False}]

From the sorted Δs it looks like about half of the participants were within 50 places or so of their seeds, while a few were way off (in both directions).

BarChart[Sort[swimΔ]]

Median[Abs@swimΔ]

N[Mean[Abs@swimΔ]]

56.70099667774086`

N[StandardDeviation[Abs@swimΔ]]

51.80100030247153`

Commonest[Abs@swimΔ]

{16}

tally = Sort[Tally[Abs@swimΔ]]

{{0, 5}, {1, 3}, {2, 4}, {3, 3}, {4, 1}, {5, 6}, {6, 6}, {7, 6}, {8, 5}, {9, 4}, {10, 5}, {11, 1}, {12, 5}, {13, 3}, {14, 4}, {15, 5}, {16, 10}, {17, 1}, {18, 4}, {19, 3}, {20, 5}, {21, 4}, {22, 6}, {23, 4}, {24, 3}, {25, 1}, {26, 5}, {27, 2}, {28, 4}, {30, 6}, {31, 2}, {32, 4}, {33, 2}, {34, 6}, {35, 4}, {36, 2}, {37, 2}, {41, 5}, {42, 2}, {43, 2}, {44, 3}, {45, 3}, {46, 2}, {47, 2}, {48, 3}, {49, 3}, {50, 3}, {51, 5}, {52, 3}, {53, 1}, {54, 1}, {55, 1}, {56, 3}, {57, 4}, {58, 2}, {59, 2}, {60, 2}, {62, 4}, {63, 3}, {64, 1}, {65, 2}, {66, 2}, {67, 4}, {68, 1}, {69, 1}, {70, 1}, {71, 2}, {72, 1}, {75, 2}, {76, 1}, {77, 1}, {79, 2}, {80, 1}, {83, 2}, {86, 3}, {88, 1}, {90, 5}, {94, 1}, {96, 1}, {97, 2}, {101, 1}, {105, 1}, {106, 2}, {108, 1}, {111, 1}, {113, 1}, {114, 3}, {116, 1}, {117, 1}, {118, 1}, {121, 2}, {122, 3}, {123, 4}, {125, 1}, {128, 1}, {130, 1}, {131, 1}, {133, 1}, {134, 1}, {135, 2}, {136, 2}, {141, 1}, {143, 1}, {146, 1}, {151, 1}, {156, 1}, {157, 1}, {158, 1}, {159, 1}, {160, 1}, {161, 1}, {163, 1}, {167, 1}, {168, 2}, {170, 1}, {172, 1}, {174, 1}, {177, 1}, {179, 1}, {186, 1}, {188, 1}, {194, 1}, {195, 1}, {197, 1}, {205, 1}, {226, 1}, {277, 1}}

BarChart[Range[0, Max[tally[[All, 1]]]]/.Append[Apply[Rule, tally, 1], _Integer->0], FrameLabel->{TraditionalForm[Abs["swimΔ"]], "Count"}, Frame->{True, True, False, False}]

It looks like most people were 40-50 places off (in one direction or the other) from their seed. This is higher than I would have expected. The most common difference was 16 places. There must have been a lot of passing going on.

Download Mathematica Notebook

My first WebKit patch

2009-04-24T17:24:00.000-05:00

Several years ago I spent a few hours implementing a feature in Mozilla, and then probably 10 times that amount of time dealing with the hassle of getting my code (which I was trying to give them for free) approved and into their sources. The incident left a bitter aftertaste.

Fast forward to present day. I was just reading through some WebKit sources and noticed a typo in one of the comments. So I decided to fix the typo and submit a patch to see how painful the process is for the competing project.

Index: JavaScriptCore/ChangeLog
===================================================================
--- JavaScriptCore/ChangeLog	(revision 42833)
+++ JavaScriptCore/ChangeLog	(working copy)
@@ -1,3 +1,9 @@
+2009-04-24  Rob Raguet-Schofield  
+
+        Reviewed by NOBODY (OOPS!).
+
+        * wtf/CurrentTime.h:
+
 2009-04-23  Mark Rowe  
 
         With great sadness and a heavy heart I switch us back from YARR to WREC in
Index: JavaScriptCore/wtf/CurrentTime.h
===================================================================
--- JavaScriptCore/wtf/CurrentTime.h	(revision 42833)
+++ JavaScriptCore/wtf/CurrentTime.h	(working copy)
@@ -36,7 +36,7 @@ namespace WTF {
 
     // Returns the current system (UTC) time in seconds, starting January 1, 1970.
     // Precision varies depending on a platform but usually is as good or better 
-    // then a millisecond.
+    // than a millisecond.
     double currentTime();
 
 } // namespace WTF

Picky? Sure. But why not?

Update: patch approved after 5 hours.

Video on Aiptek PocketCinema

2009-04-20T22:33:00.001-05:00

The documentation for the Aiptek PocketCinema pico-projector claims to support the following video formats:

- MJPEG AVI (recommended)
- MPEG-4 ASF

So how do I convert video into one of these formats on a Mac with QuickTime Pro?

Test: Use QuickTime Player to Export Movie to MPEG-4.
Result: FAIL. PocketCinema hangs when attempting to preview video and needs to be reset by removing battery.

Test: Use QuickTime Player to Export Movie to AVI. MJPEG is not support. Try uncompressed, BMP, and Cinepak.
Result: FAIL. PocketCinema recognizes AVI file, does not hang, but also does not play any of the files (uncompressed, BMP, or Cinepak).

Test: Use QuickTime Player to Export Movie to QuickTime Movie with Motion JPEG codec.
Result: FAIL. PocketCinema does not recognize .mov file.

Test: Use QuickTime Player to Export to MPEG-4, then use Flv Crunch to convert to MPEG-4 again.
Result: Success! Apparently the projector has a problem with the MPEG4 generated by QuickTime, but does not have a problem with the MPEG4 generated by ffmpeg.

Behind the scenes Flv Crunch is just using the ffmpeg command line tool. The following command did the trick for me:

ffmpeg -i source.mp4 dest.mp4

Mapping GPS Data

2009-04-17T12:27:00.001-05:00

I have written a blog entry titled Mapping GPS Data that has just been posted to the Wolfram Research blog.

Twittering with Mathematica

2009-04-16T21:28:00.001-05:00

A couple weeks ago James Rohal wrote about "Updating Twitter from Mathematica." His technique is interesting, but it has a number of drawbacks. It requires special PHP code to run on his server. The user name and password appear to be hardcoded. The only functionality it provides is updating the status.

Twitter has a REST API which can be called directly from a number of languages, including Mathematica. Several months ago I started, but didn't finish, a Mathematica package to wrap the Twitter API. After I read James' post I took the opportunity to clean it up and fill in the missing pieces.

Let's take a look a few of the things this Twitter package can do. Begin by loading the package in the usual manner.

<<Twitter`

TwitterSession

Next we'll open a session. This will bring up a login dialog.

session = TwitterSessionOpen[]

TwitterSession[<ragfield>]

TwitterSessionAuthorizedQ[session]

True

TwitterSessionScreenName[session]

ragfield

TwitterSessionClose[session]

It's also possible to specify the user name and/or login programatically to avoid the manual step. However, doing so will require a hardcoded password.

session = TwitterSessionOpen["User"->"ragfield"]

TwitterSession[<ragfield>]

TwitterUser

The next object is a user. The session is associated with the user who logged in.

user = TwitterSessionUser[session]

TwitterUser[<ragfield>]

We can query the user for several attributes.

TwitterUserID[user]

12920162

TwitterUserName[user]

Rob Raguet-Schofield

TwitterUserScreenName[user]

ragfield

TwitterUserLocation[user]

Urbana, Illinois

TwitterUserHomePage[user]

http://rob.ragfield.com

TwitterUserDescription[user]

My name is Rob. I write software, ride bicycles, and occasionally write software while riding bicycles.

TwitterUserProfilePage[user]

http://twitter.com/ragfield

TwitterUserInfo[user]

Name Rob Raguet-Schofield
Location Urbana, Illinois
Web http://rob.ragfield.com
Bio My name is Rob. I write software, ride bicycles, and occasionally write software while riding bicycles.

And all this information can be displayed graphically with hyperlinks, tooltips, etc.

TwitterUserUI[user]

TwitterStatus

The final, and perhaps most important, object is the status. A status can be accessed directly by its unique ID, or it can be retrieved from a timeline (see below).

status = TwitterStatus[671394002]

TwitterStatus[<ragfield: shopping for underpants>]

We can also query the status message for several attributes.

TwitterStatusID[status]

671394002

TwitterStatusUser[status]

TwitterUser[<ragfield>]

TwitterStatusDate[status]

Sat 2 Feb 2008 19:02:02

TwitterStatusText[status]

shopping for underpants

TwitterStatusPage[status]

http://twitter.com/ragfield/statuses/671394002

TwitterStatusSource[status]

mobile web

TwitterStatusUI[status]

Setting the status

We can set our status.

status = TwitterSetStatus[session, "Tweeting from Mathematica"]

TwitterStatus[<ragfield: Tweeting from Mathematica>]

TwitterStatusUI[status]

We can also delete any of our tweets if we decided we don't like them.

status = TwitterSetStatus[session, "I am dumb"]

TwitterStatus[<ragfield: I am dumb>]

id = TwitterStatusID[status]

1537789527

TwitterDeleteStatus[session, status]

TwitterStatus[<ragfield: I am dumb>]

TwitterStatus[id]

FetchURL::"conopen": "\!$\*StyleBox[\"\\\"The connection to URL \\\"\", \"MT\"]$\!$\*StyleBox[\!\(\"http://twitter.com/statuses/show/1537789527.xml\"$, \"MT\"]\)\!$\*StyleBox[\"\\\" cannot be opened. If the URL is correct, you might need to configure your firewall program, or you might need to set a proxy in the Internet connectivity tab of the Preferences dialog (or by calling SetInternetProxy). For HTTPS connections, you might need to inspect the authenticity of the server's SSL certificate and choose to accept it.\\\"\", \"MT\"]$"

$Failed

The tweet has been deleted, so any attempt to download it again fails.

Timelines

A list of status messages can be retrieved from a specific user.

Take[TwitterUserTimeline[user], 4]

{TwitterStatus[<ragfield: Tweeting from Mathematica>], TwitterStatus[<ragfield: testing...>], TwitterStatus[<ragfield: 4 mile recovery/photo walk>], TwitterStatus[<ragfield: Marge, if anyone asks, you require 24 hour nursing care, Lisa's a clergyman, Maggie is seven people, and Bart was wounded in Vietnam>]}

Column[TwitterStatusUI/@%]

And more...

Take[TwitterUserTimeline[user, "Page"->2], 4]

{TwitterStatus[<ragfield: off to run the marathon. wish me luck.>], TwitterStatus[<ragfield: @esmithrunner good luck to you and your family as well>], TwitterStatus[<ragfield: It's just another race>], TwitterStatus[<ragfield: Little Miss C (kindergarten) after successfully adding 95+3, "I probably know just about all maths.">]}

Column[TwitterStatusUI/@%]

And even other users' timelines...

Take[TwitterUserTimeline["lancearmstrong"], 3]

{TwitterStatus[<lancearmstrong: The Armstrong's in the snow! Just went swimming at the aspen rec center.>], TwitterStatus[<lancearmstrong: http://twitpic.com/3ffo8>], TwitterStatus[<lancearmstrong: This is AMAZING!!!! http://tinyurl.com/d7d6ex>]}

Column[TwitterStatusUI/@%]

And the friends timeline...

Take[TwitterFriendsTimeline[session], 3]

{TwitterStatus[<cabel: Enjoying the absurdity of Remi Gaillard's real-life Pac-Man. http://tinyurl.com/dm9mor>], TwitterStatus[<danielpunkass: I suggest opt-in per tweet. I get a message from @twitshirt: "Lucky you! Somebody wants to make you famous!" Per-tweet licensing agreement.>], TwitterStatus[<danielpunkass: Feel bad for @twitshirt guys, but I agree it's a smarmy premise ¬©-wise. Friend in IRC suggested opt-in + @messages inviting opt-in. Solved.>]}

Column[TwitterStatusUI/@%]

And any replies to the user...

Take[TwitterReplies[session], 3]

{TwitterStatus[<spoonshake: @ragfield Ah, priceless Simpsons quotes.>], TwitterStatus[<gutzville: @ragfield I would just be happy if they put the curtis road exit in that has been open for more than a year>], TwitterStatus[<spoonshake: @ragfield Priceless headline.>]}

Column[TwitterStatusUI/@%]

And the public timeline...

Take[TwitterPublicTimeline[], 3]

{TwitterStatus[<lastp1acechamps: @mchowes yah my friend seriously lives right across the street from the newbury store and he couldn't get up for me.>], TwitterStatus[<exult: Some things alarm me more than other things>], TwitterStatus[<HambyDavid: Phone is dying. Need car charger>]}

Column[TwitterStatusUI/@ %]

Friends and Followers

Finally we can get a list of our friends and followers.

Take[friends = TwitterFriends[session], 5]

{TwitterUser[<bmeyaard>], TwitterUser[<quickKarl2>], TwitterUser[<_Becca_Knight>], TwitterUser[<bikefriday>], TwitterUser[<aimeekandrac>]}

Take[followers = TwitterFollowers[session], 5]

{TwitterUser[<bmeyaard>], TwitterUser[<quickKarl2>], TwitterUser[<NaturalComedy>], TwitterUser[<akw279>], TwitterUser[<Modells_Coupons>]}

And since this is Mathematica, we can do interesting data explorations.

friendIDs = TwitterUserID/@friends;
followerIDs = TwitterUserID/@followers;
union = Intersection[friendIDs, followerIDs];

55% of the people I'm following also follow me.

N[Length[union] / Length[friendIDs]]

0.55`

42% of the people who follow me are people whom I also follow.

N[Length[union] / Length[followerIDs]]

0.41509433962264153`

TwitterSessionClose[session]

Downloads

Download Twitter.m.

Download HTTP.m (required by Twitter.m).

Download Mathematica Notebook.

Update: I have written a very similar entry for my company's blog.

Some useful bookmarklets

2009-04-06T21:55:00.001-05:00

In case you don't know, bookmarklets are bookmarks which run JavaScript code rather than open a specific web page. Here are a collection of bookmarklets I use on a semi-regular basis to speed up searching of frequently used web sites. Bookmarklets can do other things, since they run arbitrary JavaScript code.

To install them click on the hyperlink and drag it to your bookmarks bar (or maybe right/control-click on the link and choose a menu item to add to bookmarks). They may not work in all browsers, but these all work in Safari.

You can use them in one of two ways. First, if you just choose the bookmark it will pop up a dialog asking for the query text, then search the corresponding site for the text you enter. Second, you can select a piece of text on the current web page, then when you choose the bookmarklet it will automatically search the corresponding site for the selected text.

Wikipedia

javascript:x=''+getSelection();if(!x.length){x=prompt('Wikipedia:','')}if(x&&x.length){location.href='http://en.wikipedia.org/w/wiki.phtml?search='+escape(x)}

Dictionary

javascript:x=''+getSelection();if(!x.length){x=prompt('Dictionary:','')}if(x&&x.length){location.href='http:/dictionary.reference.com/search?q='+escape(x)}

Thesaurus

javascript:x=''+getSelection();if(!x.length){x=prompt('Thesaurus:','')}if(x&&x.length){location.href='http:/thesaurus.reference.com/search?q='+escape(x)}

Google Images

javascript:x=''+getSelection();if(!x.length){x=prompt('Google%20Images:','')}if(x&&x.length){location.href='http://images.google.com/images?hl=en&q='+escape(x)}

Google News

javascript:x=''+getSelection();if(!x.length){x=prompt('Google%20News:','')}if(x&&x.length){location.href='http:/news.google.com/news?q='+escape(x)}

Google Maps

javascript:x=''+getSelection();if(!x.length){x=prompt('Google%20Maps:','')}if(x&&x.length){location.href='http://maps.google.com/?q='+escape(x)}

IMDB

javascript:x=''+getSelection();if(!x.length){x=prompt('IMDB:','')}if(x&&x.length){location.href='http:/imdb.com/Find?for='+escape(x)}

Amazon

javascript:x=''+getSelection();if(!x.length){x=prompt('Amazon:','')}if(x&&x.length){location.href='http://www.amazon.com/exec/obidos/external-search/?keyword='+escape(x)}

eBay

javascript:x=''+getSelection();if(!x.length){x=prompt('eBay:','')}if(x&&x.length){location.href='http://search.ebay.com/search/search.dll?query='+escape(x)}

Font outlines and 3D text

2009-04-06T09:09:00.001-05:00

When importing PDF files Mathematica 6-7 converts glyphs to polygons. We can utilize this fact to get outlines of these glyphs which can be further processed as desired. Here I will show how to make arbitrary font/glyph combinations into 3D objects.

NOTE: this code depends on a specific behavior of Mathematica's PDF import feature. This code may break if future versions of Mathematica change the way glyphs from PDF files are imported.

As I mentioned previously, Mathematica's PDF import simulates polygons/paths with holes by connecting the different segments/contours with 0-width lines. There is a break in a contour where these 0-width lines occur. This first function finds the points which comprise the 0-width lines.

FindContourBreaks[pts_List] := Module[
    {i, lines, breaks = {}},
    lines = {pts[[#[[1]]]], pts[[#[[2]]]]}& /@
        Partition[RotateLeft[Flatten[{#, #}& /@
            Range[Length[pts]], 1]], 2];
    For[i = 1, i <= Length[lines], i++,
        If[MemberQ[lines, {lines[[i, 2]], lines[[i, 1]]}],
            AppendTo[breaks, i]
        ];
    ];
    breaks
];

This function returns a list of the individual polygon contours.

FindContours[pts_List] := Module[
    {breaks, ranges},
    breaks = FindContourBreaks[pts];
    ranges = Partition[RotateLeft[Join[{1, 1},
        Flatten[{#, # + 1}& /@ breaks]]], 2];
    ranges = Drop[ranges, - 1];
    DeleteCases[Take[pts, #]& /@ ranges, x_ /; Length[x] < 3]
];

Now that we have a list of the contours we can process them further. Here I will convert them from a 2D polygon to a object. The top of the object will be the 2D polygon living in 3D space. The bottom will be the reverse of the top (to get the lighting correct) offset a certain depth below the top. Finally, I will add a sequence of rectangles orthogonal to the top and bottom to form the sides of the object to close it in.

ThreeDContour[pts_List, depth_] := Module[
    {topPts, botPts, sideRects, sidePts, sideNormals},
    topPts = {#[[1]], #[[2]], 0}& /@ pts;
    botPts = (# + {0., 0., - depth})& /@ topPts;
    sideRects = Partition[RotateLeft[Flatten[{#, #}& /@
        Range[Length[topPts]], 1]], 2];
    sidePts = {
        topPts[[#[[1]]]], botPts[[#[[1]]]],
        botPts[[#[[2]]]], topPts[[#[[2]]]]
    }& /@ sideRects;
    Polygon /@ sidePts
];

ThreeDContours[pts_List, depth_] := Module[
    {contours},
    contours = FindContours[pts];
    ThreeDContour[#, depth]& /@ contours
];

ThreeDPolygon[Polygon[pts_List], depth_] := Module[
    {topPts, botPts, sidePolys},
    topPts = {#[[1]], #[[2]], 0}& /@ pts;
    botPts = Reverse[(# + {0., 0., - depth})& /@ topPts];
    sidePolys = ThreeDContours[pts, depth];
    {Polygon[topPts], Polygon[botPts], EdgeForm[], sidePolys}
];

This function converts a 2D graphics scene to a 3D graphics scene where all the 2D polygons are made into 3D objects with the given depth.

ThreeDGraphics[gfx_Graphics, depth_] :=
    gfx /. Polygon[pts_List] :> ThreeDPolygon[Polygon[pts], depth] /.
        (PlotRange -> _) :> PlotRange -> All /.
            Graphics[gfx2D___] :> Graphics3D[gfx2D];

These final two functions will take an arbitrary piece of text in an arbitrary font, export it to PDF, import the PDF back into Mathematica (to convert the glyphs to outlines), and make them 3D.

ThreeDText[str_String, family_String:"Times", depth_:10] :=
ThreeDGraphics[TwoDText[str, family], depth];

TwoDText[str_String, family_String:"Times"] :=
First[ImportString[ExportString[Cell[str, FontSize -> 100,
FontFamily -> family], "PDF"], "PDF"]];

Finally, we can see the results.

ThreeDText["Hello\nWorld"]

We could also build an interface that allows us to choose which glyph in which font we want.

Manipulate[
    Show[
        ThreeDText[FromCharacterCode[character], font, depth],
        ImageSize->{Automatic, 300}
    ],
    {{font, "Times"},
        Map[First, FE`Evaluate[FEPrivate`GetPopupList["MenuListFonts"]]]},
    {{character, 65}, 33, 127, 1},
    {{depth, 10}, 0, 100}
]

Download Mathematica Notebook

Horrible Visual Studio 2008 Standard Edition installer bug

2009-04-05T11:57:00.001-05:00

I spend nearly all my time working on a Mac. Given the nature of cross-platform development I do sometimes require use of a Windows machine. Not too long ago I was upgrading to Visual Studio 2008 when I found a horrible bug in the installer.

I didn't want any Visual Basic or C# crap littering my machine. So I disabled those options, leaving only the C++ tools to be installed. Installation completed and I fired up the compiler only to get the following error message:

Compiling...
Project : error PRJ0003 : Error spawning 'cl.exe'.

Uh.

That's not supposed to happen.

Let's take a closer look:

C:\Program Files\Microsoft Visual Studio 9.0\VC\bin>dir
 Volume in drive C has no label.
 Volume Serial Number is 104F-0033

 Directory of C:\Program Files\Microsoft Visual Studio 9.0\VC\bin

04/05/2009  09:48 AM    <DIR>          .
04/05/2009  09:48 AM    <DIR>          ..
04/05/2009  09:46 AM    <DIR>          1033
04/05/2009  09:48 AM    <DIR>          amd64
11/08/2007  08:19 AM           165,376 atlprov.dll
11/08/2007  08:19 AM            77,312 bscmake.exe
11/08/2007  08:19 AM           670,192 c1.dll
11/08/2007  08:19 AM         2,334,200 c1xx.dll
11/08/2007  08:19 AM            33,784 cvtres.exe
11/08/2007  08:19 AM            17,920 dumpbin.exe
11/08/2007  08:19 AM            17,920 editbin.exe
11/08/2007  08:19 AM            17,912 lib.exe
11/08/2007  08:19 AM           790,008 link.exe
06/05/2006  06:02 PM               268 link.exe.config
11/08/2007  08:19 AM           358,384 ml.exe
11/08/2007  08:19 AM            94,200 nmake.exe
11/08/2007  08:19 AM            20,480 undname.exe
03/07/2007  03:44 PM                31 vcvars32.bat
04/05/2009  09:48 AM    <DIR>          x86_amd64
11/08/2007  08:19 AM            40,448 xdcmake.exe
06/05/2006  06:02 PM               268 xdcmake.exe.config
              16 File(s)      4,638,703 bytes
               5 Dir(s)  12,399,824,896 bytes free

So, no C++ compiler with C++ installation. Perfect.

On the suggestion of a coworker I also installed the C# tools. Low and behold the C# tools included the C++ compiler, and my problems went away:

C:\Program Files\Microsoft Visual Studio 9.0\VC\bin>dir
 Volume in drive C has no label.
 Volume Serial Number is 104F-0033

 Directory of C:\Program Files\Microsoft Visual Studio 9.0\VC\bin

04/05/2009  10:43 AM    <DIR>          .
04/05/2009  10:43 AM    <DIR>          ..
04/05/2009  09:46 AM    <DIR>          1033
04/05/2009  09:48 AM    <DIR>          amd64
11/08/2007  08:19 AM           165,376 atlprov.dll
11/08/2007  08:19 AM            77,312 bscmake.exe
11/08/2007  08:19 AM           670,192 c1.dll
11/08/2007  08:19 AM         2,334,200 c1xx.dll
11/08/2007  08:19 AM         2,356,720 c2.dll
11/08/2007  08:19 AM           125,936 cl.exe
06/05/2006  06:02 PM               268 cl.exe.config
11/08/2007  08:19 AM            33,784 cvtres.exe
11/08/2007  08:19 AM            17,920 dumpbin.exe
11/08/2007  08:19 AM            17,920 editbin.exe
11/08/2007  08:19 AM            17,912 lib.exe
11/08/2007  08:19 AM           790,008 link.exe
06/05/2006  06:02 PM               268 link.exe.config
11/08/2007  08:19 AM           358,384 ml.exe
11/08/2007  08:19 AM            94,200 nmake.exe
11/08/2007  08:19 AM            20,480 undname.exe
03/07/2007  03:44 PM                31 vcvars32.bat
04/05/2009  09:48 AM    <DIR>          x86_amd64
11/08/2007  08:19 AM            40,448 xdcmake.exe
06/05/2006  06:02 PM               268 xdcmake.exe.config
              19 File(s)      7,121,627 bytes
               5 Dir(s)  12,437,422,080 bytes free

I find it fairly shocking that this configuration was never tested before the bits left Microsoft.

Video with telemetry data overlay

2009-04-03T00:51:00.001-05:00

At my cycling team's training camp last weekend I used my Flip video camera to record video of some of the hill descents. Several teammates thought it would be neet to see the video with telemetry data (such as speed) overlayed on top of it. Since I had my GPS recording at the time it was a straightforward matter to create such a video. Here's how I did it.

In preparation I exported my GPS data to a GPX file, which Mathematica can import. Next, I used QuickTime Player Pro to convert the movie into a sequence of PNG images, which Mathematica can import.

Set the working directory to this notebook's directory for convenience.

SetDirectory[NotebookDirectory[]];

Import the data from the GPX file.

xml = Import["Descent.gpx", "XML"];

Pull out all the "trkpt" elements.

trkpts = Cases[xml, XMLElement["trkpt", _, _], Infinity];
Length[trkpts]

204

First[trkpts]

XMLElement[trkpt, {lat->37.6150774, lon->-89.2330897}, {XMLElement[ele, {}, {222.6824951}], XMLElement[time, {}, {2009-03-29 16:09:18}]}]

Extract the latitude/longitude/elevation/time from each trackpoint.

latitudes = ToExpression["lat" /. #[[2]]]& /@ trkpts;
longitudes = ToExpression["lon" /. #[[2]]]& /@ trkpts;
elevations = Cases[trkpts, XMLElement[
"ele", _, {e_String}] :> ToExpression[e], Infinity];
dates = Cases[trkpts, XMLElement[
"time", _, {t_String}] :> DateList[t], Infinity];

pts = Transpose[{latitudes, longitudes, elevations}];

Compute the distance between each successive trackpoint.

distances = GeoDistance[
GeoPosition[#[[1]], "WGS84Original"],
GeoPosition[#[[2]], "WGS84Original"]
]& /@ Partition[pts, 2, 1];

Compute the time interval between each successive trackpoing.

times = First[DateDifference[#[[1]], #[[2]], "Second"]]& /@
Partition[dates, 2, 1];

Speed = distance/time. Convert from Meter/Second to Mile/Hour.

<<Units`

speeds = (Convert[# Meter/Second, Mile/Hour] Hour/Mile)& /@
distances/times;

Since there are more video frames than GPS trackpoints we're going to want to know what the speed is between trackpoints. To do this we'll create an InterpolatingFunction. At any time between two trackpoints we'll estimate the speed to be a linear interpolation between the speed at those two points.

absoluteTimes = Drop[AbsoluteTime /@ dates, 1];

interp = Interpolation[Transpose[{absoluteTimes, speeds}]];

For each frame of the video we will import the PNG file, compute the speed for that frame of video, draw the speed on top of the video, then export the new frame.

processFrame[i_Integer] := Module[
    {label, istr, img, g},
    label = ToString@NumberForm[
        interp[First[absoluteTimes]+i*1/29.97], {Infinity, 2}];
    label = StringJoin[label, " mph"];
    istr = IntegerString[i, 10, 4];
    img = Import[StringJoin["Descent", istr, ".png"]];
    g = Show[
        Rasterize[img],
        Graphics[Style[{
            Text[label, Scaled[{0.5, 0.1}], {0, 0}],
            Style[Text[label,
                Offset[{-4, 4}, Scaled[{0.5, 0.1}]], {0, 0}]
            , FontColor -> White]
        }, FontSize -> 72]]
    ];
    Export[StringJoin["DescentProcessed", istr, ".png"], g];
    g
];

processFrame[1]

Call the processFrame[] function for each frame (and wait a potentially long time).

With[{start = 1, stop = 9606}, Monitor[
Do[processFrame[i], {i, start, stop, 1}],
ProgressIndicator[Dynamic[(i - start)/(stop - start)]]
]]

Once all the frames have been exported we can recombine them back into a single movie using QuickTime Player Pro.

Download Mathematica Notebook

Xcode project templates for MathLink applications

2009-04-02T22:22:00.001-05:00

Setting up an Xcode project to build MathLink applications can be confusing and tedius. Therefore I have created Xcode project templates for MathLink applications.

Download the templates here. Install the "MathLink" directory into "/Library/Application Support/Developer/Shared/Xcode/Project Templates/". After installation, when you create a new project in Xcode there will be a User Templates section that contains a MathLink subsection. Click on MathLink and find the two project templates.

The first project template is called C MathLink Program. Use it for the very simplest of applications where you want to implement a function (or a few functions) in C/C++ and call it directly from Mathematica. The project will create a single executable (.exe extension, yes, .exe, yes, on Mac).

Build the target and begin using it in Mathematica with the Install command.

Note: if Mathematica is installed in a different location than /Applications/Mathematica.app you will need to adjust the value of the user defined MATHEMATICA build setting in the target info window.

l = Install["~/Desktop/MyTest/build/Debug/MyTest.exe"]

LinkObject[/Users/schofield/Desktop/MyTest/build/Debug/MyTest.exe, 153, 9]

LinkPatterns[l]

{MyTest[arg1_Integer, arg2_Real, arg3_String]}

MyTest[23, 4.5, "67"]

The second project template is called C MathLink Package. Use it for more complicated applications that require both C/C++ code and supporting Mathematica code. The support code goes into init.m.

FlickrCalendar

2009-03-31T23:08:00.001-05:00

I take (at least) one photo each day and designate it my Photo of the Day. I have a set on Flickr with all of these photos and I thought it would be interesting to look at these in a calendar layout. I wrote a simple Mathematica package to do some basic photoset and photo management on Flickr. Using this package it is a simple matter to download all the Photos of the Day for a given month and arrange them in a calendar layout.

Load the Flickr package.

<<Flickr`

Get a list of all my photosets.

Short[sets = FlickrPhotosets[]]

{72157610604254463->Photo of the Day, <<22>>, 72157609839542329->S…on}

Get the ID of each photo in the "Photo of the Day" set.

set = First[sets]

72157610604254463->Photo of the Day

photos = FlickrPhotosetPhotos[set,
{2009, 3, 1, 0, 0, 0}, {2009, 4, 1, 0, 0, 0}]

{3320801525, 3325013076, 3327845866, 3330214268, 3332574152, 3333951749, 3336286979, 3339612210, 3343616292, 3346180622, 3347410349, 3349861835, 3352196443, 3355574796, 3358281254, 3361319213, 3364753768, 3366450803, 3368858991, 3372005764, 3374713192, 3377655879, 3381457738, 3384282674, 3386926438, 3389038038, 3390498631, 3394129518, 3396858987, 3400094291, 3402856851}

Length[photos]

Import the 75x75 pixel "Square" sized thumbnail of each photo.

squares = FlickrPhotoImport[#, "Square"]& /@ photos;

First[squares]

Overlay the day of the month on top of each thumbnail.

tiles = Table[
    Show[Rasterize[squares[[i]]],
        Graphics[{
            White, Opacity[0.667],
            FontSize -> 64,
            Text[ToString[i], {Center, Center}]
        }]
    ], {i, Length[squares]}
];

First[tiles]

Get the URL of each image and make the tiles hyperlinks.

urls = First["urls" /. FlickrPhotoInfo[#]]& /@ photos;

First[urls]

http://www.flickr.com/photos/ragfield/3320801525/

tiles = Table[Hyperlink[tiles[[i]], urls[[i]]], {i, Length[tiles]}];

Now write a reusable calendar[] function which takes a list of content and lays them out into a grid for the specified month.

daysInMonth[year_Integer, month_Integer] := Part[
    {31,
    Which[
        Mod[year, 400] === 0, 29,
        Mod[year, 100] === 0, 28,
        Mod[year, 4] === 0, 29,
        True, 28
    ], 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}, month
];

calendar[
    year_Integer,
    month_Integer,
    content_List,
    opts___
] := Module[
    {startDate, startDay, daysOfWeek, days},
    startDate = {year, month, 1, 0, 0, 0};
    startDay = DateString[startDate, "DayNameShort"];
    daysOfWeek = {"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"};

    (*
    if the month starts in the middle of the week
    prepend some empty strings to the content list
    *)
    days = Join[Table["",
        {Position[daysOfWeek, startDay][[1,1]] - 1}], content];

    (*
    if less content was specified than days in the month
    pad the end of content list
    *)
    days = Join[days, Table["",
        {daysInMonth[year, month] - Length[content]}]];

    (*
    if the month ends in the middle of the week
    append some empty strings to the content list
    *)
    days = Join[days, Table["",
        {Mod[7 - Mod[Length[days], 7], 7]}]];

    GraphicsGrid[
        Join[
            {Join[{Text[Style[
                    DateString[startDate,
                        {"MonthName", " ", "Year"}],
                    FontFamily -> "Times",
                    FontSize -> 48
                ]]},
                Table[SpanFromLeft, {6}]
            ]},
            Partition[days, 7]
        ],
        opts
    ]
];

Now add the tile images to the calendar.

c = calendar[2009, 3, tiles,
Spacings -> 0, ImageSize -> 460,
Dividers -> All, Background -> LightGray]

We could export directly to JPEG, but since the image contains hyperlinks exporting to HTML will yield both a JPEG and the HTML code for an image map.

SetDirectory[CreateDirectory["/tmp/FlickCalendar"]];

Export["FlickCalendar.html", c, "GraphicsOutput" -> "JPEG"];

Download Mathematica Notebook

Download Flickr Mathematica package

Image stabilization in iMovie '09

2009-03-31T08:24:00.001-05:00

I got the chance yesterday to try out the new image stabilization feature in iMovie '09. It works. Sort of.

Last weekend I strapped my Flip video camera onto the handlebars of my bike while descending a big hill. The resulting footage was pretty jerky. I started iMovie for the first time and it decided to build thumbnails for what seemed like forever. Finally I was able to add my clip to a project and enable image stabilization for it. It took around two hours on my 2.2 GHz dual core MacBook Pro to process five minutes of video. Ouch.

It appears to work by cropping the image frame to give it a few extra pixels in each direction with which to work. It then attempts to match up corresponding sections of subsequent video frames. Finally, it re-expands the cropped image to fill the frame again.

With my particular video there were a few sections which it was able to successfully stabilize, but most of it couldn't be helped. In parts the video was actually worse after stabilization (due to the scaling?). Anyway, here's a brief comparison. The top image is the original (scaled down from HD) video. The bottom frame is the stabilized version from iMovie '09.

I assure you the two videos are synchronized. Notice how the iMovie (bottom) video has a noticeably smaller field of view, slightly washed out colors, and slightly more side-to-side movement, but slightly less jerkiness.

The video was easy to put together in Mathematica. First I saved each movie as an Image Sequence in QuickTime Player Pro. Then I combined the two frames using Mathematica 7's image processing functions. Then I assembled the resulting frames back into a movie using QuickTime Player Pro. Here's the Mathematica code.

processFrame[i_Integer] := Module[
    {n, n1, n2, n3, i1, i2, i3},
    n = StringJoin[IntegerString[i, 10, 4], ".png"];
    n1 = StringJoin["Descent/Descent", n];
    n2 = StringJoin["DescentStabilized/DescentStabilized", n];
    n3 = StringJoin["DescentCompare/DescentCompare", n];
    i1 = Import[n1];
    i2 = Import[n2];
    i3 = ImageAssemble[{
        {ImageResize[i1, {480, 270}]},
        {ImageResize[i2, {480, 270}]}
    }];
    Export[n3, i3]
];

With[{start = 1, stop = 9606}, Monitor[
Do[processFrame[i], {i, start, stop, 1}],
ProgressIndicator[Dynamic[(i - start)/(stop - start)]]
]]

I'll bet I could do the stabilization in Mathematica...

Expressible as the sum of two cubes

2009-03-19T22:10:00.001-05:00

Futurama episode 1ACV06 (The Lesser of Two Evils)

Bender: Hey robot, what's your serial number?
Flexo: 3370318.
Bender: No way, mine's 2716057!
(robot laughter)
Fry: I don't get it.
Bender: We're both expressible as the sum of two cubes!

Well that should be easy enough to test with Mathematica. Let's just use a brute force method to check each pair of numbers {i, j} that adds up to number n where i is in the range of 0 to the cube root of n and j is in the range of 0 to i.

flexo = 3370318;
bender = 2716057;

SumOfTwoCubes[n_Integer] :=
Catch@Do[
    If[i^3 + j^3 == n, Throw[{i, j}]],
    {i, n^(1 / 3)},
    {j, i}
];

SumOfTwoCubes[flexo]

{119, 119}

SumOfTwoCubes[bender]

So this test found the two numbers whose cubes add up to Flexo's serial number, but it did not find the two numbers whose cubes add up to Bender's serial number. Interesting. This problem must be trickier than I first thought. Indeed it is. A coworker pointed out that the first test only searches half of the possible numbers--it completely excludes negative numbers!

Okay, let's rewrite the test to include negative numbers. The absolute value of i must no longer be constrained to the cube root of n since one of the terms can be negative. We must instead search all values between -∞ and ∞. Hmm. That might take a while. Okay, instead we'll just deal with numbers whose cubes are expressible as a 32-bit signed machine integer and we'll stop the search as soon as we find the answer. Additionally, we'll have to add an additional test where the smaller of the two values (in this case j) is negative. We know it must be the smaller of the two since their sum is positive.

BetterSumOfTwoCubes[n_Integer] :=
Catch@Do[
    Which[
        i^3 + j^3 == n, Throw[{i, j}],
        i^3 + ( - j)^3 == n, Throw[{i, - j}]
    ],
    {i, (2^31 - 1)^(1 / 3)},
    {j, i}
];

BetterSumOfTwoCubes[flexo]

{119, 119}

BetterSumOfTwoCubes[bender]

{952, - 951}

Tricky television writers.

Update: Paul Abbott points out in the comments that there's a far better way to solve this problem:

Reduce[i^3 + j^3==3370318, Integers]

i==119&&j==119

Reduce[i^3 + j^3==2716057, Integers]

(i== - 951&&j==952)||(i==952&&j== - 951)

I must admit that I've never used the Reduce function before so this was a bit of a surprise to me, but a welcome one at that.

Download Mathematica notebook

Using stack based object constructors as function parameters

2009-03-18T14:18:00.001-05:00

In C++, if the type of a function parameter is a bare class or a const reference to a class then it is not necessary to pre-create an object to pass into that function. You can use one of the class' constructors in place. For example:

class Graphics;
class Point;
...
void drawPoint(Graphics& g, const Point& p);
...
// The first argument is a non-const reference,
//   so the object must already exist
// The second argument is const reference,
//   so it can be created on the spot
drawPoint(g, Point(0, 0));

The constructor for the stack based object is called first, then the function is called, then the destructor for the stack based object is called last.

This is potentially very useful when combined with auto_ptr (or similar classes):

void foo(class Bar* b);
...
// A new "Bar" object is created, passed into
//   the foo() function, then destroyed
//   automatically after foo() is called.
foo(std::auto_ptr<Bar>(new Bar(...)));

Polygons with holes in Mathematica

2009-03-18T08:40:00.001-05:00

The Mathematica graphics language has a Polygon primitive, but (as of Mathematica 7) there is no way to create a Polygon with holes punched out (more specifically, any polygon with two or more contours). However, there is a fairly good way to fake this feature.

Draw the first polygon contour.
Draw a line from the ending point of the first contour to the starting point of the second contour.
Draw the second polygon contour.
Repeat steps 1-3 for N contours
Once all contours are drawn, draw a line from the ending point of contour N-1, then N-2, ..., all the way back to contour 1. These are the same ending points we used earlier, except in reverse order.

MultiContourPolygon[polys_List] := Module[
    {contours=Append[#, First[#]]&/@polys},
    {
        Polygon@Join[Join@@contours, Reverse[First/@contours]],
        Line[contours]
    }
]

Graphics@MultiContourPolygon[{
    {{0, 0}, {0, 1}, {1, 1}, {1, 0}},
    {{.25, .25}, {.75, .25}, {.75, .75}, {.25, .75}},
    {{.4, .4}, {.6, .4}, {.6, .6}, {.4, .6}}
}]

Mathematica's built-in PDF import feature uses this same algorithm to represent arbitrary multi-contoured paths from PDF files.

Import["ExampleData/mathematica.pdf"]

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Use Quartz2D Python bindings to rasterize HTML

2009-03-17T12:45:00.000-05:00

Since (I believe) Mac OS X 10.2, the CoreGraphics framework (Quartz2D) has included incredibly useful bindings for the Python language. This makes it very easy to test code and to automate graphics related tasks.

A few days ago a colleague asked if I knew a simple way to automate the creation of image previews of web pages. In a couple minutes I whipped up a short Python script to do just that.

#!/usr/bin/python
import os, sys
from CoreGraphics import *

# what size image should we create?
w = 600
h = 430

# get the input and output file paths
if len(sys.argv) < 3:
	print 'usage: %s inputfile.html outputfile.png' % sys.argv[0]
	sys.exit()

input = sys.argv[1]
output = sys.argv[2]

# read the input file
f = open(input)
html = ''.join(f.readlines())
f.close()

# draw the HTML into a Quartz bitmap context then write that image to a PNG file
ctx = CGBitmapContextCreateWithColor(w, h, CGColorSpaceCreateDeviceRGB(), (0, 0, 0, 0))
ctx.drawHTMLTextInRect(CGDataProviderCreateWithString(html), CGRectMake(0, 0, w, h))
ctx.writeToFile(output, kCGImageFormatPNG)

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Unfortunately, this simple script has a fairly major limitation. It doesn't do any network access, so the HTML file and all accompanying resources must be stored somewhere on your file system.