To turn on or off a Arduino digital pin, its mode is first set using pinMode() and then its state is set using digitalWrite(). For example, to turn on digital pin 5 for one second then turn if off for one second repeatedly, the following code could be used.

int myPin = 5;
void setup() {
   pinMode(myPin,OUTPUT);
}
void loop() {
   digitalWrite(myPin,HIGH);
   delay(1000);
   digitalWrite(myPin,LOW);
   delay(1000);
}

It is also possible to control the digital pins by accessing the port registers directly. For example, the following achieves the same result as the above code. It is explained below.

void setup() {
   DDRD = DDRD | B00100000; 
}
void loop() {
   PORTD = PORTD | B00100000;
   delay(1000);
   PORTD = PORTD & B11011111;
   delay(1000);
}

Each port has a one byte register defining the direction of the associated pins. This register is called DDRD for port D and DDRB for port B. From zero to seven, each bit in this register corresponds to the comparably numbered pin of that port. For example, the fifth bit of DDRD controls port pin D5 or Arduino digital pin 5. If this bit is set to zero, the pin is an input. If this bit is set to one, the pin is an output pin. Thus, the line of code in the setup function above sets Arduino digital pin 5 to an output pin using a bitwise or operator. Each port also has a one byte register defining the state of the associated pins. This register is called PORTD for port D and PORTB for port B. Just like the DDRx registers, each bit in these registers from zero to seven corresponds to the comparably numbered pin of that port. For example, the fifth bit of PORTD controls the state of pin D5 or Arduino digital pin 5. If this bit is set to zero, the pin is set to 0 V. If this bit is set to one, the pin is set to 5 V (on the Arduino Uno). Thus the lines of code in the loop function above first turns on Arduino digital pin 5 using a bitwise or and then turns this pin off using a bitwise and.

Controlling digital i/o pins at the register level is incredibly powerful. For example, you could turn all 8 pins of port D using a single line of code if you wanted to. However, with great power comes great responsibility. Manipulating registers can be tricky and may yield unexpected results. For example, buried in the ATmega328 data sheet is a warning that one can not change a pin from the high impedance input off state to the output on state in one step. You must first go to an intermediate state of output low or input high before going to output high.

In order for two devices to communicate via a serial signal, both must be configured with the same baud rate or bits per second (bps) rate. This tells both machines the interval of time between individual bits so they can synchronize. The most common baud rate for Arduino is 9600. In fact, this is the default baud rate when a new serial monitor is opened from the Arduino IDE. Other baud rates are sometimes necessary. For example, communication with GPS modules often uses a baud rate of 4800.

The following sketch demonstrates serial communication between an Arduino Uno and a the serial monitor on a computer. When a character is sent to the Arduino from the serial monitor on a computer, the Arduino reads this byte and immediately will send it back. The Serial.begin(), Serial.available(), Serial.read(), Serial.print(), and Serial.write() commands are used to start serial communication, test to see if any bytes are available in the serial buffer, read in the next byte in the serial buffer, print a decimal number to the serial monitor, and print the ASCII character corresponding to this decimal number, respectively. The comments in the code should help you figure out what each component does.

// Program Name: Serial Echo

// note: serial bytes are read as ASCII 
// (American Standard Code for Information Interchange) 
// characters

byte myByte; // a variable to store a byte read from the serial 
// buffer

void setup() {
  Serial.begin(9600); // begin serial communications at 9600 bps
}

void loop() {
 if (Serial.available()>0) {
  while(Serial.available()>0){ // while bytes remain in the serial 
  // buffer
  myByte = Serial.read(); // read in the current byte
  // = is ASCII character 61
  // 0-9 are ASCII characters 48 to 57
  // - is ASCII character 45
  // + is ASCII character 43
  }
  Serial.print("ASCII Character Value of Byte Read: \n");
  Serial.write(myByte);
  Serial.print('\n');
  Serial.print("ASCII Decimal Value of Byte Read: \n");
  Serial.print(myByte); // prints ASCII character corresponding 
  // to myByte
  Serial.print('\n');
 }
}

One important concept to understand is that serial information is sent out of and read into the Arduino one byte at a time. Moreover, each byte that is read into memory corresponds to the decimal ASCII encoding for the ASCII character being received. So, if the character A is sent, the value stored in myByte would be 65 since this is the decimal code for the ASCII character A. For more on ASCII characters and serial communications see this post.

Since there are three colors, controlling a common-cathode RGB LED with an Arduino requires three digital output pins (and three current limiting resistors). You could turn these pins off and on one at a time using digitalWrite() commands. You could also use a byte (of which one bit controls each of the colors so five bits would be unused) and a bit-mask. See this post for more details. This would result in more compact code.

When lights of different colors are combined, new colors result. But unlike pigment mixing, which is subtractive color mixing, light mixing results in additive color mixing. Red and green makes yellow, red and blue makes magenta, and green and blue makes cyan. If red, green, and blue are simultaneously turned on, white light is produced. In order to obtain more fine grained control over the color produced by an RGB LED, you can use PWM and analogWrite() (see this post for more details).

This particular relay is a single pole, double throw (SPDT) switch. If you were controlling a switch like this with an Arduino you would hook an Arduino digital pin up to pin 2 (or pin 5) then hook pin 5 (or pin 2) up to ground. Then setting the Arduino digital pin high will throw the switch. The device being switched should be hooked up across pins 1 and 3. Notice that a SPDT switch connects pins 1 and 4 when no current is supplied across pins 2 and 5. A single pole, single throw (SPST) switch like the one shown below (also made by OMRON) lacks this alternative path. An SPST switch will be specified to be normally open (NO) or normally closed (NC). This particular relay is normally open.

int myPins[] = {2, 3, 4, 5, 6, 7, 8, 9};
int onPins = B11010010; 

void setup() {
   for (int ii = 0; ii <= 7; ii++) {
      pinMode(myPins[ii],OUTPUT);
      digitalWrite(myPins[ii],LOW);
   }
}

void loop() {
   for (int ii = 0; ii <= 7; ii++) {
      if (onPins & (B10000000 >> ii)) {
         digitalWrite(myPins[ii],HIGH);
      }
      else {
         digitalWrite(myPins[ii],LOW);
      }
   }
}

The B10000000 >> ii portion of the code uses a right bit shift operator to shift each bit in B10000000 exactly ii places to the right. For each rightward shift, the least significant bit falls off and the most significant bit is replaced by a zero. For example B10000000 >> 4 would yield B00001000.

The conditional part of the if statement uses the bitwise AND compare. Each bit of the byte contained by onPins is compared to the corresponding bit of the byte resulting after the bit shift operator (what is often referred to as the bitmask). If any of the bitwise compares evaluates true then the entire if statement evaluates true and the if statement code is executed. If none of the bitwise compares evaluate true then the if statement evaluates false and the code in the else statement is executed.

Note that the result of the bitmask is to turn on all of the pins corresponding to the 1s in onPins and turn off all the other pins.

I hope you found this quick tutorial helpful. Happy programming.

newNumber = orignialNumber*maxValueOnNewRange/maxValueOnOriginalRange

The following is the prototype Arduino sketch promised above.

int analogValue; // a place to hold the decimal value produced by 
// the ADC
float analogVolts; // a place to hold the analogValue mapped back 
// to voltage
byte analogPin = 5; // the analog pin connected to the analog 
// signal we wish to read (pin A5)

void setup() {
// nothing
}

void loop() {
analogValue = analogRead(analogPin);
analogVolts = (float)analogValue*5/1023; // must convert int to float 
// to perform floating point math
}

Let’s say you did an experiment to measure the spring constant of a spring. You systematically varied the force exerted on the spring (F) and measured the amount the spring stretched (s). Hooke’s law states the F=-ks (let’s ignore the negative sign since it only tells us that the direction of F is opposite the direction of s). Because linear regression aims to minimize the total squared error in the vertical direction, it assumes that all of the error is in the y-variable. Let’s assume that since you control the force used, there is no error in this quantity. That makes F the independent value and it should be plotted on the x-axis. Therefore, s is the dependent variable and should be plotted on the y-axis. Notice that the slope of the fit will be equal to 1/k and we expect the y-intercept to be zero. (As an aside, in physics we would rarely force the y-intercept to be zero in the fit even if we expect it to be zero because if the y-intercept is not zero, it may reveal a systematic error in our experiment.)

The images below and the following text summarize the mechanics of using LINEST in Excel. Since it is an array function, select 6 cells (2 columns, 3 rows). You can select up to 5 rows (10 cells) and get even more statistics, but we usually only need the first six. Hit the equal sign key to tell Excel you are about to enter a function. Type LINEST(, use the mouse to select your y-data, type a comma, use the mouse to select your x-data, type another comma, then type true twice separated by a comma and close the parentheses. DON’T HIT ENTER. Instead, hold down shift and control and then press enter. This is the way to execute an array function. The second image below shows the results of the function. From left to right, the first row displays the slope and y-intercept, the second row displays the standard error of the slope and y-intercept. The first element in the third row displays the correlation coefficient. I actually don’t know what the second element is. Look it up if you are interested. By the way, you might wonder what the true arguments do. The first true tells LINEST not to force the y-intercept to be zero and the second true tells LINEST to return additional regression stats besides just the slope and y-intercept.

% define the number of frames in your movie
numberOfFrames = 1200;
% use a loop to generate frames of the movie
for ii = 1:numberOfFrames
    % insert code to update data to be plotted
    % plot data
    figure(1); clf;
    plot(x,y);
    % insert code to format plot any way you want
    drawnow; % force the plot to be displayed
    M(ii) = getframe(1); % save figure 1 as an element of
    % a movie object called M
end

% use the movie2avi function to save the movie
% there are several parameters you can specify
% the only one usually worth messing with is 
% frames per second (fps)
% 20 fps will make this 1200 frame movie 60 s long
movie2avi(M, 'filename', 'fps', 20);

I hope this helps. The AVI will probably be over a GB in size. Use handbrake or ffmpeg to convert the movie made by MATLAB to a more compressed format like MP4.

R = ΔT/[(dQ/dt)/A]

where T is temperature, Q is heat, t is time, and A is surface area. The SI units for R are K m2 s/J or K m2/W however, most insulations sold in the US use the convoluted units of oF ft2 h/BTU.

The larger an insulations R-value, the better it is at slowing the flow of heat.

More insight into the meaning of R-value can be had by considering a different but equivalent definition. R-value is also the ratio of an insulations thickness over the thermal conductivity of the material from which it is made. More compactly,

R = L/k

where L is thickness and the thermal conductivity k has SI units of W/(K m) and Imperial units of BTU/(hr ft oF).

In this form, it can be seen that the thicker the insulation, the higher its R-value and the better it is at slowing the flow of heat. Two different insulations may have different R-values even if they are made out of the same material if they have different thicknesses. For this reason, R-value, like weight, is an extrinsic property of insulation. On the other hand, insulation’s thermal conductivity is an intrinsic property of the material from which it is made.

Since R-value depends only on thickness and thermal conductivity, it is additive if two or more pieces of insulation are combined. For example, if one were to sandwich two pieces of foam insulation with R-values of 5 and 8, respectively, the combination would have an R-value of 13.

The efficiency of a heat pump is highest when the difference between the indoor and outdoor temperature is the least. For this reason, air-source heat pumps are much more efficient in the spring and fall then in the winter and summer. The HSPF rating attempts to take seasonal variations in heat pump efficiency into account. For this reason, it can be thought of as an average heating efficiency over the course of a year.

HSPF is defined as the ratio of the thermal energy transferred into your home per heating season in British thermal units (BTU) divided by the electrical energy consumed by the heat pump in watt-hours (Wh) per heating season. More compactly,

HSPF = (thermal energy transfered, BTU)/(electrical energy used, Wh)

As a physicist, it doesn’t make much sense to mix two units of energy (BTU and Wh) in the same formula. It makes understanding the formula more complicated. If one notes that 1 Wh = 3.412 BTU, then

HSPF = 3.412 (thermal energy transfered)/(electrical energy used)

where the energies can be in any units so long as they are the same units. In this form, you can see that a 100% efficient electric resistive heater has a HSPF rating of 3.412. Thus a heat pump with a HSPF rating of 6.8 would pump about twice as much thermal energy into your home as it consumes in electricity.

Although the HSPF rating you will actual achieve depends on your climate (hotter climates will achieve higher real-life HSPF ratings than cooler climates) replacing a 6 HSPF heat pump with a 9 HSPF heat pump will decrease the amount of electricity needed to heat your home by about 33.3%. In general, you can calculate the percent reduction in electricity used by a new heat pump to heat your home using the following formula.

Percent Energy Savings = 1 - (Old System HSPF)/(New System HSPF)

The efficiency of a heat pump is highest when the difference between the indoor and outdoor temperature is the least. For this reason, air-source heat pumps are much more efficient in the spring and fall then in the winter and summer. The SEER rating attempts to take seasonal variations in heat pump efficiency into account. For this reason, it can be thought of as an average efficiency over the course of a year.

SEER is defined as the ratio of the thermal energy transfered out of your home per cooling season in British thermal units (BTU) divided by the electrical energy consumed by the heat pump in watt-hours (Wh) per cooling season. More compactly,

SEER = (thermal energy transfered, BTU)/(electrical energy used, Wh)

As a physicist, it doesn’t make much sense to mix two units of energy (BTU and Wh) in the same formula. It makes understanding the formula more complicated. If one notes that 1 Wh = 3.412 BTU, then

SEER = 3.412 (thermal energy transfered)/(electrical energy used)

where the energies can be in any units so long as they are the same units. In this form, you can see that a 100% efficient air conditioner has a SEER rating of 3.412. Thus a heat pump with a SEER rating of 6.8 would remove about twice as much thermal energy from your home as it consumes in electricity.

Although the SEER rating you will actual achieve depends on your climate (hotter climates will achieve lower real-life SEER ratings than cooler climates) replacing a 10 SEER heat pump with a 16 SEER heat pump will decrease the amount of electricity needed to cool your home by about 37.5%. Replacing a 10 SEER heat pump with a 22 SEER model will reduce the electricity used by your heat pump by about 54.5%. So there is diminishing returns to energy savings with increasing SEER rating. In general, you can calculate the percent reduction in electricity used by a new heat pump to cool your home using the following formula.

Percent Energy Savings = 1 - (Old System SEER)/(New System SEER)

Makeup of A Fictional Domain

Here we will consider the set up of a fictional domain named mydomain.lan on a restricted network (i.e., a LAN located behind a firewall) and the 192.168.1.0 subnet. The domain will have have 4 hosts with the following addresses, names, and roles.

IP Address          hostname     role                alias
192.168.1.99       john         DNS/mail server
192.168.1.50       paul         web server          www
192.168.1.51       george        workstation
192.168.1.52       ringo        workstation

Note that the web server is configured with the alias (canonical name) www so that one can navigate to it using www.mydomain.lan in addition to paul and paul.mydomain.lan. Of course your domain will vary in makeup and function to the one considered here, but you should be able to modify the following code to suit your needs.

Configure Zones on BIND

Ubuntu installs BIND with a configuration file /etc/bind/named.conf that suits most home office and small business needs and does not need to be modified. Instead you will create your local DNS “zone” by editing /etc/bind/named.conf.local, which is sourced by named.conf. Open this file with a text editor of your choice (I use vi here).

sudo vi /etc/bind/named.conf.local

Ignore the commented areas and add a zone definition for your domain to this file.

zone "mydomain.lan" IN {
    type master;
    file "/etc/bind/zones/mydomain.lan.db";
};

Add a reverse DNS zone definition as well. This will allow the server to map IP addresses to domain names.

zone "1.168.192.in-addr.arpa" {
    type master;
    file "/etc/bind/zones/rev.1.168.192.in-addr.arpa";
};

Create DNS Records

The zone definitions in the previous section refer to files that will contain details about our network mapping. The mydomain.lan.db file will contain records of the hostname-to-IP address mappings of your domain. The rev.1.168.192.in-addr.arpa file will contain “reverse” IP address-to-hostname records. Make a directory to hold these files and open mydomain.lan.db.

sudo mkdir /etc/bind/zones
sudo vi /etc/bind/zones/mydomain.lan.db

For the fictitious domain considered here mydomain.lan.db is edited to look like the following.

; Use semicolons to add comments.
; Host-to-IP Address DNS Pointers for mydomain.lan
; Note: The extra "." at the end of addresses are important.
; The following parameters set when DNS records will expire, etc.
; Importantly, the serial number must always be iterated upward to prevent
; undesirable consequences. A good format to use is YYYYMMDDI where
; the I index is in case you make more that one change in the same day.
mydomain.lan. IN SOA john.mydomain.lan. hostmaster.mydomain.lan. (
    200709131 ; serial
    8H ; refresh
    4H ; retry
    4W ; expire
    1D ; minimum
)
; NS indicates that john is the name server on mydomain.lan
; MX indicates that john is (also) the mail server on mydomain.lan
mydomain.lan.    IN NS  john.mydomain.lan.
mydomain.lan. IN MX 10 john.mydomain.lan.
; Set an alias (canonical name) for paul
www   IN  CNAME  paul.mydomain.lan.
; Set the address for localhost.mydomain.lan
localhost    IN A 127.0.0.1
; Set the hostnames in alphabetical order
george       IN A 192.168.1.51
john         IN A 192.168.1.99
paul         IN A 192.168.1.50
ringo        IN A 192.168.1.52

After creating the reverse DNS record file

sudo vi /etc/bind/zones/rev.1.168.192.in-addr.arpa

it is edited to look like the following.

; IP Address-to-Host DNS Pointers for 192.168.1.0 subnet
@ IN SOA  john.mydomain.lan. hostmaster.mydomain.lan. (
    200709131 ; serial
    8H ; refresh
    4H ; retry
    4W ; expire
    1D ; minimum
)
; define the authoritative name server
IN  NS   john.mydomain.lan.
; our hosts, in numeric order
99        IN PTR john.mydomain.lan.
50        IN PTR paul.mydomain.lan.
51        IN PTR george.mydomain.lan.
52        IN PTR ringo.mydomain.lan.

Of course, your DNS records will look different then those above but hopefully by using these configurations as templates you can customize the files to your domain. To initiate your authoritative DNS server restart BIND.

sudo /etc/init.d/bind9 restart

Test your DNS server by typing dig mydomain.lan at the command prompt. All of the hosts on your local network should appear under AUTHORITY SECTION in the output of this command.

Step 1: Install BIND DNS server on Ubuntu

There are two ways to install BIND on Ubuntu. If you are performing a fresh installation of Ubuntu Server Edition as per this post, at some point the install shell will ask if you wish to install a DNS and/or LAMP server. Select DNS (and LAMP if you so desire using the arrow keys and spacebar) and continue (using tab and enter). On the other hand, if you have already completed the installation of your LAMP server then use Ubuntu’s built in package management program apt-get to install BIND. Open a terminal and type

sudo apt-get update
sudo apt-get install bind9

You may need to insert the Ubuntu install CD to perform this installation.

Step 2: Configure BIND Caching DNS server

By default, BIND installs on Ubuntu configured to act as a caching DNS server. However, you need to edit the configuration options file /etc/bind/named.conf.options to specify a public DNS server operating on the wide area network (WAN) to which un-cached domain names should be forwarded. Open this file with the text editor of your choice (I use vi here).

sudo vi /etc/bind/named.conf.options

Uncomment and edit the forwarders section of this file to point to your internet service provider’s DNS server. You may enter multiple DNS server addresses (separated by semicolons) if you desire. When finished, the forwarders section should look like the following with the xxx.xxx.xxx.xxx replaced with the appropriate IP address(es).

forwarders {
xxx.xxx.xxx.xxx;
xxx.xxx.xxx.xxx;
};

You must also edit the /etc/resolv.conf configuration file of all machines on your LAN (including the DNS server itself) to point to your new DNS server. Open this file

vi /etc/resolv.conf

and add

nameserver xxx.xxx.xxx.xxx

to the top of the file where xxx.xxx.xxx.xxx is the IP address of your new DNS server. When configuring the DNS server itself, change the nameserver address to 127.0.0.1, which points to localhost. You may delete any additional nameserver lines appearing in the resolv.conf file although it may be prudent to leave lines in place that point to your ISP’s DNS server so that client machines continue to function in the event of your server going offline (just make sure your DNS server is listed first). To implement the changes to your DNS server, restart BIND.

sudo /etc/init.d/bind9 restart

Finally, test your server by typing the following command in a terminal on any machine on your LAN configured to use your new DNS server.

dig www.fiz-ix.com

Near the end of the output of this command there should be a line that reads Query time: 24 ms (of course the actual time may be different). Execute the dig www.fiz-ix.com command again and you should notice that the query time significantly decreased indicating that your DNS server is caching DNS information for www.fiz-ix.com. Note that BIND caches DNS information to RAM and not disk. In most cases this will not be a problem since most machines have plenty of memory and old records are purged from memory after a period of time. However, if you expect your server to get a lot of traffic you may want to periodically flush the cache using

sudo rndc -s localhost flush

or set the maximum amount of memory to use (in essence forcing overflow data to be deleted before it expires) by setting the max-cache-size option in the configuration file.

Congratulations! you are finished setting up your Ubuntu caching name server. See my next post where I discuss configuring a master DNS server to serve hostnames to machines on your LAN.

Because this is a google spreadsheet, it can be run on any computer with an internet browser and does not require expensive software like Microsoft Excel. To use the spreadsheet, simply enter the ticker symbol for the company you want to investigate on the ‘Summary’ sheet and press enter. The code automatically downloads ten years of financial data and calculates a per share value for the company. This spreadsheet does in 5 seconds what used to take me about an hour. There are several preferences you can modify to change how conservative you wish to be in your analysis. Click here to download the spreadsheet. The images below are examples of the output generated by the spreadsheet.

My spreadsheet is free while other valuation spreadsheets on the internet cost money (see for example Old School Value) because of its simple design and limited functionality, and I am offering it without a guarantee that it will work for all companies. I tested it and it works for most of the DJIA companies so long as they had (mostly) positive owner earnings during the last ten years. You probably don’t want to invest is companies that have had negative owner earnings recently anyways. It is meant for academic purposes only and any investing decisions should be based on a thorough analysis of the prospective company’s financial statements and fillings. That said, if you have any problems with the spreadsheet, leave a comment on one of my stock valuation posts and I will try to help you out.

CLICK HERE TO DOWNLOAD

You must have a Google account to view and copy the spreadsheet. The spreadsheet is initially read only. Open the spreadsheet and select File > Make a copy... and save it to your Google Drive with whatever name you wish. Now you can change the ticker symbol and default parameters to begin valuing companies.

In a previous post, I shared step-by-step instructions for setting up a Ubuntu LAMP (Linux, Apache, mySQL, PHP) server on your local area network (LAN). I also showed how you could customize the server installation to include all of the niceties of Ubuntu’s Desktop GUI. If this installation was successful, you should be able to view the default site served by Apache (actually an index of the default site) using any machine on your LAN. Type the server’s IP address (or alias if you added the server to your /etc/hosts file) in your browser’s address bar or, if you are browsing on the server itself, type 127.0.0.1 or localhost. If an error occurs, then you will have to edit the apache2.conf file to ensure that Apache can fully resolve the server’s name. Out of good measure you should do this anyway, even if everything seems to be working. Use your favorite text editing program (I use vi here) and open the file.

sudo vi /etc/apache2/apache2.conf

Add the following line somewhere:

ServerName localhost

and restart Apache.

sudo /etc/init.d/apache2 restart

If the default site loads then you are ready to configure Apache to serve your own sites. This configuration process may not be familiar to you if someone else hosts your websites. Here I walk you through the necessary steps. Additionally, I show you how to install phpMyAdmin to administer mySQL databases and how to configure a cgi-bin directory to run CGI programs.

Step 1: Create a new Apache site

To create a new site, first create a directory where you want to keep files associated with this site. I like to keep sites in my home directory so (using my user name of jeff) I create a /home/jeff/public_html directory. The configuration files for all sites available to Apache are stored in the /etc/apache2/sites-available/ directory. Create a configuration file for your new site (here called fiz-ix) by copying the configuration file for the default site.

sudo cp /etc/apache2/sites-available/default /etc/apache2/sites-available/fiz-ix

Open the new configuration file.

sudo vi /etc/apache2/sites-available/fiz-ix

You will notice that there is a lot of stuff between <VirtualHost> tags. You have to edit some of this. Change the DocumentRoot path to point to the newly created site directory.

DocumentRoot /home/jeff/public_html

In a similar fashion, change one of the Directory directives (it looks something like this)

<Directory /var/www/>

to be consistent with your site path.

<Directory /home/jeff/public_html/>

After making these changes, disable the default site using the Apache disable site script.

sudo a2dissite default 

Next, use the Apache enable site script to activate the new site.

sudo a2ensite fiz-ix

Finally, restart Apache.

sudo /etc/init.d/apache2 restart

Create a simple index.html file and save it in /home/jeff/public_html/ to test your new site. Something simple like

<html>
<strong>Fiz-ix is Fun</strong>

Browse (preferable on another machine) to your new site to test the configuration.

Step 2: Install phpmyadmin and create root mySQL user

In order to make mySQL database administration easy, many hosts provide phpMyAdmin. You can easily install this tool on your Ubuntu LAMP server too using the built in package management software. At the command prompt type

sudo apt-get update
sudo apt-get install phpmyadmin

You may have to insert the Ubuntu install CD to complete this installation. During the installation the script will ask which version of Apache to automatically configure. If you installed apache as per this previous post then select apache2 (with space bar) and continue. After the install completes, the phpMyAdmin script should be in the /usr/share/directory and (after restarting Apache; see above) it should resolve in your browser when you type localhost/phpmyadmin (or xxx.xxx.xxx.xxx/phpmyadmin). If it doesn’t, you must add the following alias and include to the bottom of the apache configuration file apache2.conf in /etc/apache2/.

Include /etc/phpmyadmin/apache.conf
Alias /phpmyadmin /usr/share/phpmyadmin

You can log in by using root as your username and the root password configured during the mySQL installation (if you decided not to enter a mySQL password or were not prompted for a password then the password field is blank by default). Once logged on to phpMyAdmin, you can set a new root password by navigating to the privileges page, clicking the icon that looks like a pencil next to each root account (there may be more than one), and entering a password in the appropriate field of the page that loads.

Step 3: Configure a cgi-bin directory

Configuring Apache to allow CGI program execution is pretty easy. Create a directory to be used for CGI programs (here I create /home/jeff/public_html/cgi-bin) and add the following to the site configuration file (again between the <VirtualHost> tags).

ScriptAlias /cgi-bin/ /home/jeff/public_html/cgi-bin/
<Directory /home/jeff/public_html/cgi-bin/>
          Options ExecCGI
          AddHandler cgi-script cgi pl
</Directory>

The first line creates an alias that points to the directory in which CGI scripts are stored. The final line tells Apache that only files that end with the *.cgi and *.pl extensions should be considered CGI programs and executed.

Congratulations! Your new site is configured. It is worth mentioning that if you are going to be granting computers on the wide area network access to your new Ubuntu LAMP server, you should take some time to learn how to properly secure Apache. Check out these other sites for more information on configuring Apache under Ubuntu. Ubuntu Community, Apache2.2 Documentation

Disclosure: I am long MSFT

Use this automated google spreadsheet to quickly value companies you are thinking of investing in. The spreadsheet using a twenty-year discounted cash flow method like the method Warren Buffet uses. To use the spreadsheet, simply enter the ticker symbol for the company you want to investigate on the ‘Summary’ page and your preferences and the code automatically downloads five years of financial data and calculates a per share value for the company. This spreadsheet does in 5 seconds what used to take me about an hour.

Click on the link below to get the spreadsheet. You must have a Google account to view and copy the spreadsheet. It is initially read only. Open the spreadsheet and select File > Make a copy... and save it to your Google Drive with whatever name you wish. Now you can change the ticker symbol and default parameters to begin valuing companies.

LINK TO SPREADSHEET

I can not guarantee that the spreadsheet will work for all companies. I tested it and it works for all of the DJIA companies so long as they have positive cash-flow for the last five years. You don’t want to invest is companies that have had negative cash flow recently anyways. It is meant for academic purposes only and any investing decisions should be based on a thorough analysis of the prospective company’s financial statements and fillings. That said, if you have any problems with the spreadsheet, leave a comment below and I will try to help you out.

Disclosure: I am long INTC