Re: st: RE: Loop question

[Alberto R Osella <arosella@irccsdebellis.it>]

Thank you Nick. You are right. I found the mistake and now the loop runs 
well.
Thank you again.
Alberto

Alberto R. Osella, MD, PhD
Laboratorio di Epidemiologia e Biostatistica
IRCCS Saverio de Bellis
Via Turi, 27
70013 Castellana Grotte (BA)
Italia
Tel:    +39 0804994655
Fax:    +39 0804994650
e-mail: arosella@irccsdebellis.it


Il 08/02/2011 11:06, Nick Cox ha scritto:
> Strictly, I don't know that P_B4_cut is a variable. It might be a variable; it might be a scalar; it might not exist. There is no way to tell from this posting. But whatever the story, -xtile- won't run because it needs a varname.
>
> Nick
> n.j.cox@durham.ac.uk
>
> Nick Cox
>
> Stata is telling you the problem. It is nothing to do with the loop as such, but a problem with the syntax of -xtile-.
>
> The -cutpoint()- option expects a variable.
>
> P_R1 - P_B4_cut is not a variable; it is an expression, specifically the difference between two variables. Therefore, you must create a variable holding this difference before you enter the loop.
>
> Alberto R Osella
>
> after a factor analysis (pca)  I'd want to create categorical variables
> by using a loop. But I have some troubles. Here the code I'm using
>
> predict P_R1 P_R2 P_R3 P_R4, regression
> predict P_B1 P_B2 P_B3 P_B4, bartlett
>
> foreach x of var  P_R1-P_B4 {
> pctile q_`x'_c= `x' if caso_ctrol0==0&   P_R1-P_B4<., nq(5)
> tab2 `x' caso_ctrol0
> xtile `x'_q=`x', cutpoint( P_R1-P_B4_cut)
> tab2 `x'_q caso_ctrol0
>      }
> and this is the error:
> variable P_B4_cut not found
> in option cutpoints()
> r(111)
> I'm using Stata 11.1 on windows 7.
>
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