Re: st: if command

[Nick Winter <nw53@cornell.edu>]

There is no easy way to get around testing the condition twice.  But you 
could simplify the code a bit like this:

. gen byte big = (fpi == "big") if !missing(fpi)
. gen var1 = 1 if big==1
. gen var2 = 1 if big==1
. gen var1 = 2 if big==0
. gen var2 = 12 if big==0

This doesn't reduce the number of tests of the -if- condition, but it does 
simplify considerably the coding.  Depending on what your concern is, this 
might be a good solution.

--Nick Winter


At 11:13 AM 1/18/2005 -0500, you wrote:

> Hello
>
> What is the best way to achieve the following in stata? I have a 
> reasonably complex logical test and number of new variables to generate as 
> a result of applying the test. Here is a minimal example. The real problem 
> is more complex, but this captures the spirit:
>
> gen var1 = 1 if fpi == "big"
> gen var2 = 1 if fpi == "big"
> replace var1 = 2 if fpi == "small"
> replace var2 == 12 if fpi =="small"
>
> Repeating the condition seems inefficient especially if it was very 
> complex (it is) and if I have to create many new variables (I do). I was 
> thinking some like this:
>
> if fpi == "big" {
>         gen var1 = 1
>         gen var2 = 1
> }
> if fpi == "small {
>         replace var1 = 2
>         replace var2 = 12
> }
>
> Not much of a saving in this example, but in a more complex problem the 
> saving would, I think, be measurable. However, I know from experimentation 
> and from a previous thread that this code does not work as expected. Is 
> there a solution or should I should I just use the first coding style? 
> Thanks in advance.
>
> Cameron
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