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Re: st: editing string variables to remove letters and keep only numbers

From   "Darren White" <>
To   <>
Subject   Re: st: editing string variables to remove letters and keep only numbers
Date   Tue, 18 Jun 2013 09:05:31 +1000


I would use "destring" with the " force" option (which would return you a variable with only the numeric IDs).
You could then remove those IDS from your string vars (using if conditions) , perform your routine (below)  then bring back the non-alpha prefixed id's from your destring variable.


Darren White BSc MPH 
Preventive Health Unit
Chief Health Officer Branch
Department of Health
Butterfield Street

Herston 4006
ph: (07) 3328 9288
mobile:0407 094 595

>>> Michael McCulloch <> 6/18/2013 8:53 am >>>
I have a variable in my dataset that (due to changes in data entry practices over time) contains several styles of the variable ID:

- a number (e.g. 164)
- a letter-number combination (e.g. e64)
- a comma-separated letter-number combination (e.g. e64,e65) 

In seeking to (A) remove the letters, and (B) separate the comma-separated into two separate variables, ID1 and ID2, I wrote the following argument:

. split ID, p(",")
. gen str id1_new =""// make new ID to separate out the "e" from ID
. replace id1_new=substr(id1,2,3) 

This successfully splits ID into ID1 and ID2.

This also works if: 
a 3-digit variable has a preceding letter (e64 is changed to 64)

However, in the case of a 3-digit values WITHOUT PRECEDING LETTER, the first digit is removed (164 is changed to 64).

Any suggestions would be appreciated.

Best wishes,
Michael McCulloch, LAc MPH PhD

Pine Street Foundation, since 1989
124 Pine Street | San Anselmo | California | 94960-2674  
P: (415) 407-1357 | F: (206) 338-2391 | 

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