- Data Sets in Stata

- Interactive Use
- Reading in a Stata dataset
- Reading in a Non-Stata dataset (a csv file)
- Summary statistics
- Linear Regression
- Twoway scatterplot with fitted regression line
- Stata do-file (A Script or program or Batch File)
- Help in Stata

**STATA ACCESS AT U.C.-DAVIS**

Some but not all UCD computer labs have Stata.

Schedules are available at http://clm.ucdavis.edu/rooms/

You need a campus computing account: https://computingaccounts.ucdavis.edu/cgi-bin/services/index.cgi

Stata stores data in a special format that cannot be read by other
programs.

Stata data files have extension .dta

Stata can read data in several other formats.

A standard format is a comma-separated values file with extension .csv (which can be created by Excel
for example).

INTERACTIVE
USE

This is similar to using Excel.

[Additionally one can combine commands in a file and execute the file.

This faster method for more experienced users is presented at the end of this file].

Interactive use can be initiated in several ways

- Click on the Stata icon in MS windows
- Click on the name of a file containing a Stata dataset (with extension .dta)
- Click on the name of a file containing a Stata do-file (with extension .do)

Commands can be entered using the menus and consequent dialog boxes at the top.

Or commands can be typed in the Command line at the bottom.

READING IN A STATA DATA SET

Consider data in the Stata date file carsdata.dta

Here we suppose the file is in directory C:\stata (so the file is C:\stata\carsdata.dta)

1. The simplest method is in Windows go to the directory with file carsdata.dta and double-click on carsdata.dta

This initiates Stata and opens the data file.

2. Alternatively start STATA in Windows.

In the command line give the commands

cd C:\stata

use carsdata.dta

or even more simply give the command

use "C:\stata\carsdata.dta"

3. Alternatively start STATA in Windows.

Use the File Menu and the Open submenu and browse to find the file and click on the file.

For more details see statareadinstatadataset.html

In all cases we obtain

READING IN A NON-STATA DATA SET: A CSV FILE

Stata can read in some other types of data file than a Stata dataset.

It cannot read in an Excel spreadsheet (with extension .xls or .xlsx).

A standard alternative format is a comma-separated file or comma-delimited file (with extension .csv).

For example in Excel an Excel worksheet can be saved as a .csv file.

An example is file carsdata.csv

Start STATA in Windows.

In the command line give the commands

cd C:\stata

insheet using carsdata.csv

or even more simply give the command

insheet using "C:\stata\carsdata.dta"

Alternatively Use the File Menu and the Import submenu.

Choose ASCII data created by a data sheet

And browse to find the .csv file and click on the file.

SUMMARY
STATISTICS

To obtain summary statistics we can simply type in the command
line

summarize

and hit <enter>.

Alternatively we can use the Stata Statistics menu and subsequent
submenus:

Then hit on summary statistics to get:

To obtain summary statistics for all variables simply hit the OK button.

This yields

There are five observations on two variables: cars and hhsize.

Summary statistics provided are the mean, standard deviation, minimum
and maximum.

Additional statistics would have been displayed if we had checked
Display additional statistics.

LINEAR REGRESSION

To regress variable cars
on variable hhsize
simply type in the command
line

regress
cars hhsize

and hit <enter>.

Then choosing Linear Regression yields a dialog box that we fill out as follows:

Hit OK (or directly give command regress cars hhsize) yields output

The estimated regression line is

cars = 0.8 + 0.4*hhsize

TWOWAY SCATTERPLOT WITH FITTED REGRESSION LINE

This can be obtained using the command

twoway (scatter cars hhsize) (lfit cars hhsize)

Alternatively use the Graphics menu and the Twoway Graph (scatter, line, etc.) submenu.

STATA DO-FILE (A Script or program or Batch File)

Stata commands can be combined in a text file with extension .do called a do-file.

The file carsdata.do has the following text

* Stata do-file carsdata.do written January 2009

* Create a text log file that stores the results

log using carsdata.txt, text replace

* Read in the Stata data set carsdata.dta

use carsdata.dta

* Describe the variables in the data set

describe

* List the dataset

list

* Provide summary statistics of the variables in the data set

summarize

* Provide an X,Y scatterplot with a regression line

twoway (scatter cars hhsize) (lfit cars hhsize)

* Save the preceding graph in a file in PNG (portable networks graphic) format

graph export carsdata.png

* Regress cars on hhsize

regress cars hhsize

The lines beginning with * are explanatory comments that are ignored by Stata.

To run this do-file simply click in Windows on filename carsdata.do

This file needs to be in the same directory as file carsdata.dta

Alternatively, start Stata, give command cd C:\stata (if file carsdata.do and carsdatat,dta are in directory C:\Stata)

and then give command

do carsdata.do

The program does the preceding analysis.

Results are put in the text file carsdata.txt

HELP IN STATA

Stata provides extensive documentation on-line.

For example, to obtain help on the command summarize, in the command
line type

help summarize

Alternatively use the Help menu

For further information on how to use STATA go to

http://cameron.econ.ucdavis.edu/stata/stata.html