Stata:^® Version 8

Description
Where to find Stata
Stata: Instructions
Common Problems
Other resources
If you still need help

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

The current release of Stata is Stata 8. Consistent with Stata policy, version 8 is compatible with earlier releases of Stata, meaning that syntax you might have used with Stata 7 or earlier should work with Stata 8 just as it did with earlier releases. But, to assure compatability, be sure to put version 7.0 at the top of your old syntax files.

There are several new features in Stata 8. These include --

Graphics enhancement: Stata graphics have been completely overhauled. Old graphics commands work with the graph7 command. See the graphics manual Stata Graphics Reference Manual for details.
Dataset format: The format of Stata stystem files has changed to accommodate longer storage types. If you send a Stata dataset to a Stata 7 user, be sure to use the saveold command.
Multiple missing values: Stata 8 adds capacity to define more than one value for each variable to be missing.
Faster executime times: Stata 8 executes commands in about half the time used by Stata 7 for the same commands.
Statistical procedures: Several statistical methods, including time series analysis, survival analysis, cross-sectional time-series analysis, cluster analysis, and survey analysis, contain significant upgrades.
New in expressions and functions: Many changes and upgrades have been added to Stata commands. Examples include: missing values allowed in matrix expressions, new distribution functions, no missing values returned by density or distribution functions.

The list of upgrades is lengthy. For more information, see the Stata User's Guide, Section 1.3. "What's new."

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Where to find Stata

Stata for UNIX may be used on the central UNIX server, strauss, but Stata is not available on copland. This document describes use of Stata on UNIX.

Stata for Windows is installed in the Research Data Management Services (RDMS) Lab located in the basement of Smith Hall, Room 002C.

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Stata: Instructions

On UNIX, 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 interface such as an X-terminal, a UNIX Workstation, or an emulation of an X-terminal such as Exceed running on Windows or MacX running on a Mac.

To start full-screen Stata, logon to strauss and type --

xstata8

at the UNIX prompt. Three panes appear in a new window. Figure 1 shows an image of the Stata 8 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. Figure 2 shows a simple example. The upper left pane displays the Stata commands and commands that were entered in the lower right pane. The lower left pane lists the names of the variables, and the Stata Results window, upper right, displays the output.

To show a high-resolution histogram, type, for example --

graph twoway 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 --

stata8

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 

    price mpg weight 
  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 the 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, just 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

substituting the name of your file for filename. 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 --

use mpgtest
describe

To run Stata using this command file, type --

stata8 -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 the do keyword, 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 a file named stata.log for diagnostics.

You can accomplish the same result by using the UNIX redirection symbols, like this --

stata8 < 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 devides 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. However, this command is ignored unless you run the batch command file using the -b do flag.

To run the job in the background, use the UNIX "&" character at the end of the command. For example --

stata -b do mpgtest &

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Common Problems

There are no known problems.

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Other Resources

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. To get started with help, type help without a command name.
Search command: search search topic

Refer to Stata printed documentation:

StataCorp. 2003, Stata User's Guide: Release 8, College Station, TX: Stata Corporation
StataCorp. 2003, Stata Reference Manual: Release 8 (4 volumes), College Station, TX: Stata Corporation
StataCorp. 2003, Stata Graphics Manual: Release 8, College Station, TX: Stata Corporation
StataCorp. 2003, Stata Time-Series Reference Manual: Release 8, College Station, TX: Stata Corporation
StataCorp. 2003, Stata Cross-Sectional Time-Series Reference Manual: Release 8, College Station, TX: Stata Corporation
StataCorp. 2003, Survival Analysis and Epidemiological Tables: Release 8, College Station, TX: Stata Corporation
StataCorp. 2003, Stata Cluster Analysis: Release 8, 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.

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If You Still Need Help

If you need help quickly, you may call the IT Help Center. at 831-6000 between 8:00 a.m and 5:00 p.m. Monday through Friday. Or you can submit a question through e-mail .

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