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st: -charlist- revised on SSC; question about -*trim()-


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: -charlist- revised on SSC; question about -*trim()-
Date   Sat, 30 Apr 2005 16:01:32 -0400

Daniel Egan started a thread by publicising 
a dataset in which a string variable that 
"should have been" numeric contained hard-
to-detect non-numeric characters. 

He eventually fixed his problem by editing 
the original data file within a text editor. 

He tried using, among others, the program 
-charlist- from SSC, but did not find it helpful. 

I then explained what had happened: the problem 
arose from occurrences of the non-breakable space, 
in Stata terms -char(160)-, which is hard to 
see when displayed at the end of a string. 

-charlist- had reported the occurrences nevertheless. 

What I have done is revise the help file for 
-charlist- adding and explaining this very 
interesting and instructive example. Kit Baum 
kindly replaced the file on SSC. You can 
install or replace -charlist- by 

. ssc inst charlist 

or 

. ssc inst charlist, replace 

Stata 7 is required, as previously. 

This leaves an open question about -trim()-. 
In both Stata 8 and Stata 9, something like 

. gen foo = "foo" + char(160) 

adds a character that -trim()- won't remove. 

. replace  foo = subinstr(foo, "`=char(160)'", "",.) 

will do it. But I'm tempted to regard it as a limitation
of -trim()- that it won't remove -char(160)-. 

-ltrim()- or -rtrim()- raise the same issue. 

On the other hand, Daniel's report is the first 
and only report of a problem I can recall of this 
kind. 

StataCorp may have a comment. 

Nick 
n.j.cox@durham.ac.uk 


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