Re: st: identify unique string values within lists of elements over chosen time windows

[Nick Cox <njcoxstata@gmail.com>]

clear
input obs     yr   str4 var1 str4  var2 str4   var3
 1        90   str1    str2    str3
 1        91    str1    str4    str5
 2        90    str3    str4
 2        91    str4    str5
 2        93    str3    str5
 2        94    str7
end
reshape long var , i(obs yr) j(which)
bysort obs var (yr) : gen new = _n == 1 & !missing(var)
bysort obs yr : replace new = sum(new)
by obs yr : replace new = new[_N]
reshape wide var, i(obs yr) j(which)

Nick

On Thu, Mar 21, 2013 at 11:22 PM, Denisa Mindruta <mdenisa@yahoo.com> wrote:
> Hi everyone. I have an unbalanced, large panel dataset, where each observation
> can take multiple string values (each string is stored in a separate variable).
> At each point in time, I need to count whether the string value(s) taken by an
> observation are "new" , meaning that they do not show up among the values taken
> by the same observation in previous years. How should I approach  this problem ?
> Thanks !  Below is a description of data. I need to calculate newval
>
> obs     yr   var1    var2    var3    newval
> 1        90   str1    str2    str3     3
> 1        91    str1    str4    str5     2
> 2        90    str3    str4              2
> 2        91    str4    str5              1
> 2        93    str3    str5              0
> 2        94    str7                       1
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