SSC Staff: Barbara Mellert Christina Divoll, Lab Manager Kevin Grady |
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| Introduction to Stata | |||||||||
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| Stata is free software for Dartmouth students. The current version is version 9 for Windows XP and Mac OS X machines. You can get the software from: www.dartmouth.edu/software . Follow the link for your machine (Windows/Mac), and then choose “Academic Software.” You’ll find Stata in the list. In order to run the software you need a supporting application called KeyAccess. If you purchased your computer through the college, all the necessary supporting software should already be in place. If not, you’ll need to install and configure KeyAccess before you can run Stata. Check out “Using KeyAccess to Activate Software” for help with this. KeyAccess (KSClient) allows you to run keyserved applications. Keyserved applications are those where the server determines whether or not you’re authorized to use the application. The Dartmouth keyserver address is keyserver.dartmouth.edu. This must be set in the KeyAccess setup dialog. Stuffit Expander is used by the Mac download for expanding the installation package. Stata will download as a Zip file for Windows machines and as an Installer package on Mac machines. For Windows users, open Zip folder and run the stata9.msi file. When the installation is complete, launch the program via START – All Programs – Dartmouth College – Stata9 – Launch Stata9. You’ll get a message saying the program is not licensed and then a dialog box with a form to fill out. Using the information in the License.txt file contained in the Zip folder, fill out the form and license the program. For Mac users, when the download is complete, expand the package (this may happen automatically) then click on the VISE icon labeled Stat 9.0 OX X Installer. Launch the program by clicking on the Stata icon in the Stata folder in the Applications folder of your Hard Drive. If you have trouble please stop by the lab for help. When you launch Stata, you’ll see several windows that you’ll use while working with the program. Command – provides and input area for entering Stata command statements. Results – shows you the commands you’ve entered along with their results. (If “more” appears at the bottom, press ‘enter’ to continue scrolling the results or ‘q’ to quit. Review – displays a history of the most recent commands entered. Highlighting a command here will make it appear in the Command window. Variables – lists the variables contained in the current data set. Only one data set at a time can be current in Stata. Highlighting a variable in this window will make it appear in the Command window. Data Editor – displays the current data set in spreadsheet format. The data editor can also be used when cutting and pasting data to and from other spreadsheet applications like Excel. This window must be closed in order to issue commands. Graph – displays the results of graphics associated command statements. Log files keep a record of the command statements you enter and
Stata’s output. Specifying a filename saves the log to a file;
saving as a log format rather than the default SMCL format will
allow you to open the log in other applications (like Word). log using "c:\my documents\clients\hsb.log",
replace text {It’s wise to open a log file at the beginning of a session, turning it on or off as you need to save commands and results.} Stata can read the following filetypes: .dta – a data file in Stata
format Different command statements are used to load data sets in different file formats. Most commonly you’ll issue the use command to read Stata formatted data sets. File - Open menu will open a data file already in Stata format
infile will read freefield data and tab- or comma-delimited data; can have multiple records
infix will read fixed field data
{You can often cut and paste data from other applications into Stata's data editor}
clear - clears data out of memory. search – searches Stata help for matching strings. This allows you to find help on command statements and return codes which appear alongside of error messages. If you make a mistake with a Stata command, it may return an error message along with a return code {for example, r(199)}. The search command can be used to get a more detailed description of the return code.
generate – computes a new variable
based on an expression. Basic Analysis Commands tabulate - gets counts and percents of subgroups for 1 or 2 variables. Summarize option gets summary stats for subgroups.
summarize - calculates summary statistics such as mean and standard deviation. Detail option gets more statistics and percentiles. By option gets statistics for subgroups.
correlate - displays the correlation matrix for a list of variables. Means option gets summary stats for each variable.
regress – fits a linear regression
model of a dependent variable on a single predictor or set of predictors.By
the time you’re done with this class, you’ll know what
that means. Graphs graph bar – generates a bar chart histogram – generates a histogram graph twoway – generates a two variable scatterplot graph pie – generates a pie chart Graphs do not get written to the log files. They must be saved using:
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