st: RE: Problem using wildcard and renaming string variables

["Barclay Matthew (SHEFFIELD TEACHING HOSPITALS NHS FOUNDATION TRUST)" <matthewbarclay@nhs.net>]

Hi Pierre,

I am not sure whether your problem relates to filenames, variable names, or observations in a particular variable "ratingR1". I think you are trying to handle observations in a particular variable "ratingR1", and these observations are actually the filenames of various files of survey data.

What you want to do is to create two variables, one with only the observations (filenames) from survey wave 1 and one with only the observations from survey wave 2. You don't want the observations in either of these new variables to have the two character suffix.

I have two suggestions, one helpful and one not. The unhelpful suggestion is to read an introductory text on Stata programming, or to take the web course, so that you understand the syntax. The helpful suggestion is to not use a regular expression, as in this particular case it is not necessary. Some example code that should do what you want is below.


******* start example

/* generate wave identifier, containing just the 2 character suffix */
gen wave_id = substr(ratingR1,-2,.)

/* generate variable containing the length of ratingR1 */
gen length_ratingR1 = length(ratingR1)

/* replace this with one 2 shorter, so we can get rid of the suffix easily */
replace length_ratingR1 = length_ratingR1-2

/* get rid of suffix */
replace ratingR1 = substr(ratingR1,1,length_ratingR1)

/* generate wave 1 and wave 2 variables */
generate ratingR1_wave1 = ratingR1 if inlist(wave_id,"01","06","09","11","13")
generate ratingR1_wave2 = ratingR1 if inlist(wave_id,"03","05","08","12","14")

******* end example


Hope that helps,
Matt



-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Pierre Pratley
Sent: 23 July 2013 16:23
To: statalist
Subject: st: Problem using wildcard and renaming string variables

Dear colleagues,

I'm having problems renaming / removing string variables using a wildcard.
I am using Stata 11.
Basically, I have added a suffix of two numbers to filenames that are in my
database as a string variable.
The two numbers identifying survey waves are: suffixes 01, 06, 09, 11 and
13 for one round 1 and
03, 05, 08, 12 or 14 for round 2.

I'm trying to create a new variable per round, one in which the suffixes
are removed for round 1, and  observations are dropped for round 2, and
vice versa.

I have gone through statalist and help functions and it seems I need to use
a -regexr extension but am having trouble with the syntax:
drop if ratingR1 regexr(ratingR1, "*[03][05][08][12][14]$")

This should drop all values in the string variable ratingR1 that end in 03,
05, 08, 12 and 14?

And then how do I replace the values 01, 06, 09, 11 and 13?

Any help would be much appreciated. Thanks.
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