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Re: st: generate variable equal to first non-zero value in row
From
Nick Cox <[email protected]>
To
"[email protected]" <[email protected]>
Subject
Re: st: generate variable equal to first non-zero value in row
Date
Wed, 21 Aug 2013 16:54:34 +0100
Eric is right. I'll revise my post.
Nick
[email protected]
On 21 August 2013 16:51, Eric A. Booth <[email protected]> wrote:
> <>
>
> Nick's advice is slightly different than mine. His gets you the "out"
> variable with the value of interest as the value in first_nonzero --
> mine gets you value the first "out" variable holds.
> Based on the column of values the OP puts in the example dataset, I
> _think_ he wants an approach closer that what I suggested, but you can
> still use Nick's code and add this to get the values of interest
> (though I feel like there's a faster way to get there than my code
> below):
>
> forval n = 1/`=_N' {
> if !mi(`=first_nonzero[`n']') {
> replace first_nonzero = out`=first_nonzero[`n']' in `n'
> }
> }
>
> - Eric
>
> On Wed, Aug 21, 2013 at 10:35 AM, Nick Cox <[email protected]> wrote:
>> How would you do it by hand? You would look at each variable from left
>> to right until you find the first non-zero. So, Stata can be
>> instructed to do that too.
>>
>> gen first_nonzero = .
>>
>> qui forval j = 1/5 {
>> replace first_nonzero = `j' if out`j' & first_nonzero == .
>> }
>>
>> Note here that
>>
>> if `outj'
>>
>> is short-hand for
>>
>> if `outj' != 0
>>
>> and we also need the condition that
>>
>> first_nonzero == .
>>
>> If all values are zero, the variable remains set to missing.
>>
>> For a fairly detailed review of such questions, see
>>
>> SJ-9-1 pr0046 . . . . . . . . . . . . . . . . . . . Speaking Stata: Rowwise
>> (help rowsort, rowranks if installed) . . . . . . . . . . . N. J. Cox
>> Q1/09 SJ 9(1):137--157
>> shows how to exploit functions, egen functions, and Mata
>> for working rowwise; rowsort and rowranks are introduced
>>
>> which is accessible at http://www.stata-journal.com/sjpdf.html?articlenum=pr0046
>> Nick
>> [email protected]
>>
>>
>> On 21 August 2013 16:25, D-Ta <[email protected]> wrote:
>>> Dear Statausers,
>>>
>>> I have a dataset with the variables id and and out1-out5 where the "out"
>>> variables represent sequential outcomes. I would like to generate a variable
>>> (in the example below named first_nonzero) which indicates the first outcome
>>> in the sequence row that is non zero. If there are all zeros throughout,
>>> that indicator variable should be set/remain missing.
>>>
>>> The following table illustrateswhat I am trying to do. How do I generate the
>>> first_nonzero variable? (I was trying to work with the -egenmore- commands,
>>> but couldnt figure out).
>>>
>>> id out1 out2 out3 out4 out5 first_nonzero
>>> 1 0 0 0 2 2 2
>>> 2 0 2 2 0 0 2
>>> 3 0 0 0 0 0 .
>>> 4 4 4 4 0 0 4
>>> 5 3 0 2 2 2 3
>>> 6 0 4 4 4 0 4
>>>
>>>
>>> Many thanks,
>>> Darjusch
>>> *
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>> *
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> *
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