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Re: st: -if- and r() in -histogram-


From   jpitblado@stata.com (Jeff Pitblado, StataCorp LP)
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: -if- and r() in -histogram-
Date   Thu, 04 Feb 2010 09:40:07 -0600

Antoine Terracol <Antoine.Terracol@univ-paris1.fr> is using an -if- condition
with -histogram- that depends on an -r()- result, but -histogram- isn't
behaving as expected:

> I am puzzled by the fact that -histogram- does not seem to properly 
> select cases based on a comparison with a saved result after -summarize-:
> 
> /**********************/
> clear
> cap graph drop _all
> set obs 1000
> g x=exp(rnormal())
> su x, de
> local p95=r(p95)
> di r(p95)
> hist x if x<r(p95), name(ha)
> hist x if x<`p95', name(hb)
> hist x, name(hc)
> /**********************/
> 
> the first histogram (with the -if- statement and the reference to 
> r(p95)) is identical to the last histogram (without the -if- statement). 
> When r(p95) is saved to a local macro which is then used in an -if- 
> statement, it works fine (second graph).
> 
> Now, I have not tried all types of graphs, but -kdensity- seems to 
> behave as expected:
> 
> /**********************/
> clear
> cap graph drop _all
> set obs 1000
> g x=exp(rnormal())
> su x, de
> local p95=r(p95)
> di r(p95)
> kdensity x if x<r(p95), name(ka)
> kdensity x if x<`p95', name(kb)
> kdensity x, name(kc)
> /************************/

This is unintended behavior and will be fixed in a future update to Stata.

--Jeff
jpitblado@stata.com
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