Re: st: if/else command

[Ronán Conroy <rconroy@rcsi.ie>]

Ulrich Kohler wrote:

> Moreover, in SPSS "generating" and "replacing" can be done with the same
> command. In Stata there are two. -generate- generates a new variable,
> -replace- changes the contents of an existing variable. You cannot 
> generate a
> non-existing variable with -replace-.
>
> All togheter what you want might be something like this:
>
> gen age = 22 if age <= 5 & certification == 1 ;
> replace age = 30 if age >= 6 & age <= 15 & certification == 1 ;
> replace age = 40 if age >= 16 & age <= 20 & certification == 1 ;
> replace age = 50 if age > 20 & certification == 1 ;
>
> --
Another solution is to use -recode-, which is less prolix

gen age_group=age
recode age_group [recoding rules omitted] if certification==1
recode age_group [recoding rules omitted] if certification==2

Beware of the line  
replace age = 50 if age > 20 & certification == 1 
If age is missing, the condition (age > 20) is true.

I always suffix lines with

if ~missing(variable_being_manipulated)

even when I know it has no missing values. Natural gloom, I suppose. 
Ronan M Conroy (rconroy@rcsi.ie) 
Senior Lecturer in Biostatistics 
Royal College of Surgeons 
Dublin 2, Ireland 
+353 1 402 2431 (fax 2764) 
-------------------- 
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http://www.nofreelunch.org/

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