Unix program: stata

Description

Stata is a statistical software system including

Basic statistics (e.g., univariate statistics, regression, ANOVA, logistic regression)
Advanced econometric statistics (e.g., panel analysis with random coefficients, censored regression, simultaneous-equation analysis, conditional logistic regression)
Full programming capabilities, including matrix syntax
Data management capabilities
High-resolution graphics

Where to Find stata

Stata for UNIX may be used on the central UNIX server, strauss, but stata is not available on copland. UNIX Stata is located at
```
     /opt/bin/stata
```
The full-screen GUI stata is located at
```
     /opt/bin/xstata
```
To access these two applications, type the entire path at the strauss prompt, just as it appears above.

Where Can I Use stata on Campus?
- UNIX stata is available on Strauss.
  
  Stata for Windows is available in the Research & Data Management Services (RDMS) lab. Check in the User Services office (002 Smith Hall) to get an acoount on these machines.
  
  This document describes use of Stata on UNIX, and it assumes you have your PATH variable set as just described so that stata and xstata are accessible with the short commands, stata and xstata, respectively.

Instructions for Stata

How Do I run stata on Strauss?
Stata may be run (1) in a full-screen environment, (2) in line-prompt mode, or (3) batch mode.

Full-screen Mode. To run Stata interactively in full-screen mode, you must be logged onto your unix account using an X-window interface such as a SunRay, a UNIX Workstation, or an emulation of an X-window connection such as Exceed running on Windows or an xterm window running on a Mac. A free alternative to Exceed called Cygwin now is available to students. Information about Cygwin is linked from the Exceed web page.

To start full-screen Stata, logon to strauss and type --
```
xstata
```
at the UNIX prompt. Three panes appear in a new window. Figure 1 shows an image of the Stata 9 window.

You may customize the appearance of the window by clicking Prefs. For example, to change the color scheme from green on black in the "Stata Results" pane, click Prefs/General Preferences/Results.

The editor is the bottom right pane. Type Stata commands here. For example, type the following two lines --
```
sysuse auto, clear
summarize
```
Figure 2 shows the results of these two commands. The upper left pane displays the Stata commands that were entered in the lower right pane. The lower left pane lists the names of the variables, and the Stata Results pane (upper right, black background) displays the output.

For example, to show a high-resolution scatterplot with overlaid linear-regression line, type --
```
graph twoway (lfit mpg weight) (scatter mpg weight)
```
The result looks like --

You may print the plot by issuing the print command -
```
print @Graph
```
or by clicking the right mouse button on the plot and releasing on "Print Graph".

You must be in a Stata full-screen session for the plot to display. But you can create a plot, print it, or export it to a file and use the Stata shell command to display it with a unix viewer such as ghostview or xv.

Line Mode. To run a prompted Stata session but without the full-screen window, type --
```
stata
```
at the UNIX prompt. The Stata prompt is a period located at the beginning of the command line. To exit Stata, type --
```
. exit
```
at the Stata prompt. If you have unsaved work in memory, Stata will refuse to exit. You can save your worksheet, then exit --
```
. save filename
. exit
```
replacing filename with the name of your file. Stata adds an extension of .dta to your filename.

Or you can force Stata to exit without saving your data by typing --
```
. exit, clear
```
at the Stata prompt.

You may enter data at the Stata prompt by typing the keyword input followed by a list of variable names. For example --
```
input price mpg weight 
```
Stata responds with a sequence of numbered prompts (shown in red below), one for each new observation. End the input with the keyword, end
```
  1. 4697  25 1930
  2. 8814  21 4060
  3. 3667   . 2750
  4. 4099  22 2930
  5. end
```
To list the data, type list at the Stata prompt --
```
. list

     +----------------------+
     | price   mpg   weight |
     |----------------------|
  1. |  4697    25     1930 |
  2. |  8814    21     4060 |
  3. |  3667     .     2750 |
  4. |  4099    22     2930 |
     +----------------------+

.
```
Variable names must --
- Consist of letters, numerals, and underscores
- Contain no more than 32 characters
- Begin with a letter or underscore (underscore not recommended)
Notes: (1) Variable names are case sensitive. (2) A period denotes a missing numeric value.

To add more observations, type input with no variable list, for example --
```
. input
  5. 5079  24  2280 
  6. 5189  20  3280
  7. 8129  21  2750 
  8. end

.
```
List the cases again to confirm --
```
. list

     +----------------------+
     | price   mpg   weight |
     |----------------------|
  1. |  4697    25     1930 |
  2. |  8814    21     4060 |
  3. |  3667     .     2750 |
  4. |  4099    22     2930 |
  5. |  5079    24     2280 |
     |----------------------|
  6. |  5189    20     3280 |
  7. |  8129    21     2750 |
     +----------------------+

.
```
To get univariate descriptive statistics type --
```
. summarize

Variable |     Obs        Mean   Std. Dev.       Min        Max
---------+-----------------------------------------------------
   price |       7    5667.714   1997.448       3667       8814  
     mpg |       6    22.16667    1.94079         20         25  
  weight |       7    2854.286   688.7878       1930       4060  

.
```
To record your session in a file, type --
```
. log using filename, text
```
substituting the name of your file for filename. The text option is required to get a plain text file that formats properly in a text editor such as pico. The log file will be named filename.log. To stop recording commands and output in the log, type --
```
. log close
```
Batch Mode. You can run a Stata job with your commands in a command file instead of typing them interactively at the Stata prompt. Stata expects a filename extension of .do for its command files. For example, suppose a command file named mpgtest.do contains the following commands --
```
sysuse auto, clear
summarize
graph twoway (scatter mpg weight) (lfit mpg weight)
graph export mpgXweight.ps, replace
shell xv mpgXweight.ps
```
To run Stata using this command file, type --
```
stata -b do mpgtest
```
The -b do flag indicates a batch run. The do keyword indicates to Stata to execute the commands in the file named after it, in this example, mpgtest.do. Stata assumes an extension of .do if you omit it. Output for this example is saved in a file called mpgtest.log. If your output is not written or not updated, check this .log file for diagnostics.

This command file ends with a Stata shell command to display the plot using the UNIX application named xv. It works only if you use an X-window connection to strauss.

You also can run batch Stata job by using the UNIX redirection symbols, like this --
```
stata < mpgtest.do >! mpgtest.log
```
The advantage of using the UNIX redirection symbols is that you have complete control over the names of your command files and output files. But the disadvantage is that you cannot set the command delimiter.

The command to set the character that divides Stata commands is #delimit. This can be quite useful if you have commands that span more than one line, because it improves the readablity of your code. For example, to set it to the semicolon, put--
```
#delimit ;
```
at the top of your command file. Using the #delimit command, the previous example might be reformatted for easy readability like this --
```
#delimit ;
sysuse auto, clear;

summarize;

graph twoway
   (scatter mpg weight)
   (lfit mpg weight);

graph export mpgXweight.ps,
    replace;

shell xv mpgXweight.ps; 
```
However, the #delimit command is ignored unless you run the batch command file using the -b do flag.

To run the job in the background, use the & character at the end of the command. For example --
```
stata -b do mpgtest &
```

More Help

There are several sources of additional information about Stata --

Use the Stata interactive help facility. This works best from a full-screen Stata session. Click Help and follow the links. You also may type the help command in the full-screen Stata editor or from the command prompt in line mode --

Help command: help command name.

Search command: search search topic.

To get started with help, type help without a command name.
Refer to Stata printed documentation:

StataCorp. 2003, Stata User's Guide: Release 9, College Station, TX: Stata Corporation

StataCorp. 2003, Stata Reference Manual: Release 9 (4 volumes), College Station, TX: Stata Corporation

StataCorp. 2003, Stata Graphics Manual: Release 9, College Station, TX: Stata Corporation

StataCorp. 2003, Stata Time-Series Reference Manual: Release 9, College Station, TX: Stata Corporation

StataCorp. 2003, Stata Cross-Sectional Time-Series Reference Manual: Release 9, College Station, TX: Stata Corporation

StataCorp. 2003, Survival Analysis and Epidemiological Tables: Release 9, College Station, TX: Stata Corporation

StataCorp. 2003, Stata Cluster Analysis: Release 9, College Station, TX: Stata Corporation

StataCorp. 2003, Getting Started with Stata for Unix, College Station, TX: Stata Corporation
Visit the Stata web page.

One copy of each Stata manual is kept in the Research & Data Management Services (RDMS) Lab, 002C Smith Hall.

If you need help quickly, you may call the IT Help Center at 831-6000 between 8 a.m. and 5 p.m., Monday through Friday. Or, you can submit a question through e-mail.

stata

Contents

Description

Where to Find stata

Where Can I Use stata on Campus?

Instructions for Stata

More Help