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Re: st: Variables loop and deletion under certain conditions


From   Eric Booth <ebooth@ppri.tamu.edu>
To   "<statalist@hsphsun2.harvard.edu>" <statalist@hsphsun2.harvard.edu>
Subject   Re: st: Variables loop and deletion under certain conditions
Date   Thu, 12 May 2011 16:51:17 +0000

<>

Revisit -help drop- documentation. The -drop- syntax allows for a varlist OR an if condition (which drops observations, not variables), not both.  
You could use the -if- before hand like this:
************************************!
sysuse auto, clear
tostring price mpg, force replace
keep price mpg make
**
foreach varname of varlist make price mpg {
if `varname'[5]=="Buick Electra" drop `varname' 
}
************************************!
See -help ifcmd- for more on this.


- Eric


__
Eric A. Booth
Public Policy Research Institute
Texas A&M University
ebooth@ppri.tamu.edu


On May 12, 2011, at 11:29 AM, Nuno Soares wrote:

> Hi everyone,
> 
> I'm having a problem regarding a data management task. I have several
> .csv files that I need to import and treat in Stata. Each file has a
> variable number of columns (which are variables) that cannot be
> determined beforehand, and are imported into Stata as v1, v2, ...
> Also, some of these variables/columns have no data which the database
> from where they were extracted identifies with an #ERROR message in
> line 5. What I need is to delete these variables when the error
> message is present. I tried, without success,  the following piece of
> code:
> 
> foreach varname of varlist v*{
> 	drop `varname' if `varname'[5]=="#ERROR"
> }
> 
> However Stata returns the following error code:
> 
> invalid syntax
> r(198);
> 
> Any ideas of why it isn't working? This should be straightforward, but
> I can't understand why it isn't working...
> 
> Best wishes,
> 
> Nuno
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