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st: RE: Fwd: Fastest way to identify values that start and end with a 9?


From   Joe Canner <jcanner1@jhmi.edu>
To   "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu>
Subject   st: RE: Fwd: Fastest way to identify values that start and end with a 9?
Date   Thu, 3 Oct 2013 13:24:15 +0000

Evan/Paul,

I am as confused as others regarding what you are actually trying to do, but I will add this request for clarification: you say that the variables are a mixture of 8's and 9's up to a length of string(244).  This implies that they are already strings, since Stata would not be able to store a number that was 244 digits long.  Accordingly, why then do you need to convert them to string?

Regards,
Joe Canner
Johns Hopkins University School of Medicine

-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Evan DeFilippis
Sent: Thursday, October 03, 2013 5:09 AM
To: statalist@hsphsun2.harvard.edu
Subject: st: Fwd: Fastest way to identify values that start and end with a 9?

Values in my data set contain different numerical representations for "Don't Know" and "Refusal"

A "Don't Know" will always start and end with a '9', but there can be as many '9's in between as possible, up to the maximum length of a string (244).

A "Refusal" will always start with a '9' and end with an '8', and there can be as many '9's' in between as possible, up to the maximum length of a string (244).

The data set contains strings, integers, bytes, etc..

I want to be able to convert the numerical representations of 'Don't Know' and 'Refusal's' into DK and REF, respectively.

My current strategy for doing this looks like so:

quietly tostring _all, replace
ds, has(type string)
di "`r(varlist)'"
unab string_vars : `r(varlist)'
foreach j in `string_vars'  {
  quietly replace `j'= regexr(`j', "^[9]*[9]$","DK")
  quietly replace `j' = regexr(`j', "^[9]*[8]$", "REF") }

However, this is slow because it converts the entire data set into strings, which takes about 5 minutes, and then it has to do has(type
string) in order to get r(varlist) to iterate over all those strings which takes about 4 minutes.

Is there a faster way to do this that perhaps does not involve converting everything to strings?

Paul
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