Scottish Social Survey Network: Master Class 1

Data Analysis with Stata

Dr Vernon Gayle and Dr Paul Lambert23rd January 2008, University of Stirling

The SSSN is funded under Phase II of the ESRC Research Development Initiative

Introducing Stata

Windows environmentOpening and processing commands – the

do-file editorOpening and saving dataViewing data Preserving outputs (logs)Tips (and wrinkles)Further examples on our website

STATA SOFTWARE – GOOD POINTS

• Does all the simple stuff (SPSS)

• Fits many more models than standard software (esp. Longitudinal)

• Specialist survey analysis functions (Svy)

• You can get started easily (menus and help)

• Strong documentation

• There is a growing user community (lists etc)

• New features emerge almost daily

• There are good labour market opportunities (UK little known; USA well known)

Main data window

Command window – interactive use

Variable names

Review – what you’ve done

Open the do file editor (or ‘ctrl-8’) A Do File (.do)

Highlight the command and run it from the icon

(or ctrl D)

Opening and Saving Data

• use “C:\data\dataset2.dta”

• save “C:\data\dataset2.dta”

To overwrite…

• use “C:\data\dataset2.dta”, clear

• save “C:\data\dataset2.dta”, replace

variables names & descriptions

Data Windows

Data browser (can’t edit here)

Data editor (dangerous - can edit here)

Data Editor (familiar spreadsheet)

Log files (keeping track)

log using “C:\data\temp1.log”, replace

Using Stata – Some tips

• Session settings– set more off (once in command window)– set mem 64M (, permanently)

• Data overwrite– use dataset1.dta, clear– save dataset1.dta, replace

• Do not double click on .do files in windows they will crash

• Generate variables– drop varname before gen varname

• See values and labels– numlabel _all, add

• File information– codebook

Using Stata – Some tips

• File locations– global path1 "d:\lda\work\" – use “$path1\data1.dta”, clear

• Output– capture – suppresses output (*including errors*)– nolog – e.g. suppresses interactions in logit– noheader - suppresses the display of the ANOVA table etc in regression– nodots – jacknife “not a lot of people know that”

• Line breaks– /// tells Stata to read the next line too

• Looking at the data– edit– browse– list in1/10 – shows data for cases 1 to 10

STATA SOFTWARE – BAD POINTS

• Poor data visualisation (compared with SPSS etc)• In practice, survey analysis functionality comes with

limitations (complex methods but weak data) • There are some models that can’t be fitted / some

critiques of estimation procedures• Stata syntax has some quirks (set more off)• There is a growing user community, but they are

generally GEEKBOYS (like myself!)• New features emerge almost daily these are sometimes

tricky to get to grips with

Taking Stata further

• Online resources– Stata website for FAQs, manual, training– Net use and update

• Specialist modelling suites– XT – Cross sectional panel– ST – Survival data– SV – Survey data– Xtmixed - Multilevel models (v9)– GLLAMM

• Programming: .do; .ado; macros