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Re: st: RE: Loop question


From   Alberto R Osella <arosella@irccsdebellis.it>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: RE: Loop question
Date   Tue, 08 Feb 2011 11:19:00 +0100

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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