One or both of these variables is
probably a string variable. Check out -destring-.
Nick
[email protected]
S�ren O'Neill
>
> A newbie problem perhaps, but my data looks like this:
>
> pk pixels
> -------------
> 0 100
> 0 120
> 0 110
> 1 210
> 1 230
> 1 205
>
> etc ... you get the idea...
>
> running :
> ranksum pixels, by (pk)
>
> returns:
> no observations
> r(2000);
>
> However, if (instead of my own data) I use the dataset from
> http://www.stata-press.com/data/r8/fuel2 (as described in the
> [R] S-Z p. 63,
> there is no problem at all ...
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