Stata: Tips & Snippets

Last updated: January 18, 2021

ℹ️ I wrote these notes for myself as a reference, and published them here in case they are helpful for others.

Table of contents:

• Dates and times
  • Date types in Stata
  • Summary tables
  • Converting strings to SIF date
  • Extracting hours, minutes, and seconds from SIF dates
  • Getting the last day of a given month
• Working with missing data
• Reading MySQL data directly into Stata
• Using bysort to run commands over levels of a categorical variable
• Add group counts to dataset
• Add column total variable
• Calculating arbitrary percentiles
• Counting the number of distinct values of a variable
• Create value labels from another variable
• Summarizing dataset contents
• Flow control
  • For loops
• Auto-complete variable names in Sublime Text
• Colors
• Splitting up long lines
• Reloading .ado programs
• Working with very large datasets
• Suggestions? Corrections?

Dates and times

Date types in Stata

Summary tables

Source: Stata documentation

HRF = human readable form

SIF = Stata internal form

Converting strings to SIF date

// String format: 2016-09-28T09:53:38
gen double newvarname = clock(varname, "20YMD#hms")
format newvarname %tc

// String format: 2016-09-28 09:53:38
gen double newvarname = clock(varname, "20YMDhms")
format newvarname %tc

// String format: 2016-09-28
gen double newvarname = date(varname, "20YMD")
format newvarname %td

Extracting hours, minutes, and seconds from SIF dates

gen hours = hh(tcvar)
gen minutes = mm(tcvar)
gen seconds = ss(tcvar)
gen dayofweek = dow(dofc(tcvar))
gen month = month(dofc(tcvar))
gen year = year(dofc(tcvar))

Getting the last day of a given month

local yearmonth = ym(2016,2)

di %td dofm(`yearmonth' + 1) - 1
// 29feb2016

di day(dofm(`yearmonth' + 1) - 1)
// 29

Working with missing data

Use missing(varname1, varname2) rather than == . or == "". Details here.

Reading MySQL data directly into Stata

clear
set odbcdriver ansi
odbc list
odbc load, table("tablename") dsn("mysql") clear noquote

Or you can do:

odbc load, exec("select * from tablename") dsn("mysql") clear noquote

Other resources:

• ODBC setup instructions for Mac
• Using a plugin instead of ODBC

Using bysort to run commands over levels of a categorical variable

For example, if you have a categorical variable gender and a continuous variable height, and you want to run summarize by gender (summarize doesn’t support by), you can do this:

bysort gender: summarize height

Add group counts to dataset

If you want to fill in the n_group column in a dataset like this…

…you can use this command: egen n_group = count(group), by(group)

Add column total variable

This will sum a column and generate a new variable (the same for each row) with the total:

egen sumvar = sum(var)

Calculating arbitrary percentiles

centile varname, centile(70) will give you the 70th percentile for varname.

If you want this as a variable called new_varname in your dataset:

egen p70 = pctile(new_varname), p(70)

Counting the number of distinct values of a variable

* Option 1
tab varname, nofreq
display r(r)

* Option 2
inspect varlist 
display r(N_unique)

* Option 3
codebook varlist

(Source: statdaily.com)

Create value labels from another variable

net install labutil
labmask integervarname, values(stringvarname)

Summarizing dataset contents

• inspect VARNAME: “Display simple summary of data’s attributes”
• codebook VARNAME: “Describe data contents”
• Documenting and searching a Stata dataset

Flow control

For loops

foreach i in 0 1 2 {
  di `i'
}
* 0
* 1
* 2

foreach i in a b c {
  di "`a'"
}
* a
* b
* c

forval i = 0/2 {
  di `i'
} 
* 0
* 1
* 2

If you want to loop through all levels of a variable:

levelsof varname, local(levels) 
foreach l of local levels {
  whatever if varname == `l'
}

Auto-complete variable names in Sublime Text

I like writing Stata code in Sublime Text, but I miss variable auto-completion. To get a poor man’s version of this, run the ds command in Stata, and then copy and paste the results into a /* */ comment block in your .do file in Sublime.

Colors

   

Splitting up long lines

There are two ways to do this:

* Option 1
regress lnwage educ complete age c.age#c.age     /// 
        exp c.exp#c.exp tenure c.tenure#c.tenure /// 
        i.region female

* Option 2 (only works in do-files and ado-files)
#delimit ;
regress lnwage educ complete age c.age#c.age
        exp c.exp#c.exp tenure c.tenure#c.tenure
        i.region female ;
predict e, resid ;
#delimit cr

See help delimit for more details.

Reloading .ado programs

Use the -discard- command and then run -program_name-. (source)

Working with very large datasets

Stata suggests looking at ftools and gtools.

Suggestions? Corrections?

Please contact me.