Re: st: counting the cases for which the obervations of two different variables are equal

[Richard Goldstein <richgold@ix.netcom.com>]

first, note that your two-year comparison works for greater than 2 years 
also; i.e., the first comparison will be year1 v year2 while the second 
will be that same year2 v year3 -- thus, the additional command is 
unnecessary;

the additional command does not work, I think because I don't believe 
one is allowed to do if a==b==c; however, why Stata does not give an 
error message; it did give me an error message!

Rich

minimus wrote:

> Dear All,
>
> I have a question.
>
> I would like to count the number of cases for which the observations inside 
> two different variables are equal.
> That is: Suppose you have a panel dataset where the variable 'respondent 
> number' repeats itself for some years (because the same person is observed 
> for several years) and therefore the variable 'sex'  repeats itself too.
>
> So if in the column of respndent number it reads for two obervations:
>
> 1011
> 1011
>
> then the corresponding column the sex reads
>
> male
> male
> .
>
> Ok now I would like to check if the 'sex' variable is consistent in the 
> data. To do this i use the following command:
>
> count if respnr[_n] == respnr[_n+1] & aa001[_n] == aa001[_n+1]
>
>
>
> and it returns me a number, which is fine.
>
>
>
> This command returns me the number of cases where a respondent is observed 
> for any two years and the sex of the respondent was same for those two 
> years.
>
>
>
> Now, I also ask the same question for '3 consecutive' years and use the 
> following command:
>
>
> count if respnr[_n] == respnr[_n+1] == respnr[_n+2] & aa001[_n] == 
> aa001[_n+1] == aa001[_n+2]
>
>
> Although I can see in the data browser that this condition holds for many 
> observations, stata returns "0" cases.
> That is, although I determine cases where an individual is observed for 
> three years and his sex is male for those years,
> stat does not see that and return "0".
>
> Why?
>
>
>
>
>
>
>
>
>
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