Introduction to Stata 8

9. Documentation commands [GSW] 8
Stata does not need documentation commands; you need the documentation yourself. The
output becomes more legible, and the risk of errors when interpreting the output is reduced.
Data set label [U] 15.6.1; [R] label
You can give a short description of your data, to be displayed every time you open (use) data.
label data "Fertility data Denmark 1997-99. ver 2.5, 19.9.2002"
It is wise to include the creation date, to ensure that you analyse the most recent version.
Variable labels [U] 15.6.2; [R] label
You can attach an explanatory text to a variable name.
label variable q6 "Ever itchy skin rash?"
Use informative labels, but make them short; they are sometimes abbreviated in output.
Value labels [U] 15.6.3; [R] label
You can attach an explanatory text to each code for a variable. This is a two-step procedure.
First define the label (double quotes around text with embedded blanks):
label define sexlbl 1 male 2 female 9 "sex unknown"
Next associate the label sexlbl with the variable sex:
label values sex sexlbl
Use informative labels, but make them short; value labels are often abbreviated to 12
characters in output.
Most often you will use the same name for the variable and its label:
label define sex 1 male 2 female
label values sex sex
but the separate definition of the label enables you to reuse it:
label define yesno 1 yes 2 no
label values q1 yesno
label values q2 yesno
If you want to correct a label definition or add new labels, use the modify option:
label define sexlbl 9 "unknown sex" , modify
adds the label for code 9 to the existing label definition.
In output Stata unfortunately displays either the codes or the value labels, and you often need
to see them both, to avoid mistakes. You may solve this by including the codes in the labels;
this happens automatically with:
numlabel _all , add
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