Change a string variable into a set of categorical variables in one command

Question

Say I have a categorical variable, for example a country column in a table.
How can I quickly add dummy variables for each category--WITH A RELEVANT NAME?

So if the column is for country, the variable for whether the person lives in the USA would be called USA not country16 or something.

Answer 1

This is pretty easy:

/* Make some fake data */
sysuse auto, clear
gen make_only = subinstr(lower(word(make,1)),".","",.)

/* Create meaningful dummies */
levelsof make_only, clean local(makes)
foreach m of local makes {
    gen `m' = cond(make_only=="`m'",1,0)
}

However, it is probably easier to just use factor variables notation:

sencode make_only, label(make_only) replace
reg price i.make_only
list make price if make_only=="amc":make_only

Regression output will be nicely labeled, you don't create extra variables, and it's easy enough to refer to particular values.

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sencode is written by Roger Newson and is available from SSC.