Introduction to Stata 8 - (GRIPS

Numbers to strings
You want the numeric variable cprnum converted to a string variable cprstr:
generate str10 cprstr = string(cprnum , "%10.0f")
String manipulations [U] 16.3.5; [GSW] 12
Strings can be combined by +:
generate str5 svar5 = svar3 + svar2
You may isolate part of a string variable by the substr function. The arguments are: source
string, start position, length. In the following a3 will be characters 2 to 4 of strvar:
generate str3 a3 = substr(strvar,2,3)
You may substitute characters within a string. In an example above the string variable
cprstr was created from the numeric variable cprnum. However, for persons with a
leading 0 in the CPR number the string will start with a blank, not a 0. This can be
remedied by:
replace cprstr = subinstr(cprstr," ","0",1)
The upper function converts lower case to upper case characters; the lower function does
the opposite. Imagine that ICD-10 codes had been entered inconsistently, the same code
somtimes as E10.1, sometimes as e10.1. These are different strings, and you want them to
be the same (E10.1):
replace icd10 = upper(icd10)
Handling complex strings, eg. ICD-10 codes [U] 26.4
In the ICD-10 classification of diseases all codes are a combination of letters and numbers
(e.g. E10.1 for insulin demanding diabetes with ketoacidosis). This is probably convenient for
the person coding diagnoses (an extremely important consideration), but for the data handling
it is quite inconvenient. I suggest to split a 5 character ICD-10 string variable (scode) into a
one character string variable (scode1) and a four digit numeric variable (ncode4):
generate str1 scode1 = substr(scode,1,1)
generate ncode4 = real(substr(scode,2,4))
format ncode4 %4.1f
What did we obtain? Two variables: the string variable scode1 with 26 values (A to Z) and
a numeric variable ncode4 (0.0-99.9). Now identify diabetes (E10.0-E14.9) by:
generate diab=0
replace diab=1 if scode1=="E" & ncode4>=10 & ncode4="E10" & scode