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st: accessing a variable's value WRT its attached value label


From   Phil Schumm <pschumm@uchicago.edu>
To   statalist@hsphsun2.harvard.edu
Subject   st: accessing a variable's value WRT its attached value label
Date   Wed, 29 Mar 2006 11:09:54 -0600

Suppose I have a numeric variable y, and suppose it has an attached value label which maps 1 -> "yes". Now, suppose I want to count those cases for which y "is" yes (I'm clearly using "is" in the loose sense here, but I think the meaning is clear from the context). I could of course type:

count if y == 1

however if the encoding of the variable changes (i.e., if the value 1 no longer refers to "yes"), this will (silently) no longer give me what I want. Alternatively (and in many cases better), I could write:

count if y == "yes":y_label

where y_label is the name of the corresponding value label. In this case, if the encoding changes I'm still ok (assuming that "yes" is still used in the label). But what if the *name* of the value label changes? I could do this:

count if y == "yes":`:val l y'

but that's a bit ugly. So, my question is, is there a more readable alternative to the expression above?

For those interested in the use case, I am working on a large project involving a complicated data set and a lot of code to manage the data. Right now, most variables have a dedicated value label with the same name as the variable itself. However, in the future, we may wish to economize by replacing multiple labels that have equivalent definitions with a single label. This new label will clearly have a different name than the previous label(s) for at least one of the variables involved. What I'm trying to do is to make sure that the code downstream will not break if such changes are made.


-- Phil

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