Title
[U] 13 Functions and expressions
Remarks
Algebraic and string expressions are specified in a natural way using the
standard rules of hierarchy. You may use parentheses freely to force a
different order of evaluation.
For example:
. generate new = myv+2/oth
is interpreted as
. generate new = myv+(2/oth)
If you wanted (myv+2)/oth, you could type
. generate new = (myv+2)/oth
Expressions are found in several places in the Stata language; see
language. The "=exp" language element is demonstrated above with the
generate command. The "if exp" language element is another place where
expressions are allowed. Almost all Stata commands allow the "if exp".
For instance, in
. summarize mrg dvc if region=="West" & mrg>.02
the region=="West" & mrg>.02 is a logical expression.
Examples
. sysuse auto
. generate weight2 = weight^2
. webuse census12, clear
. summarize marriage_rate divorce_rate if region == "West" &
marriage_rate > .015
. drop _all
. set obs 10
. generate x = _n^3 - 10*_n^2 + 5*_n
. generate z = x + 50*rnormal()
