st: Mata query

[Adrian Mander <Adrian.Mander@mrc-hnr.cam.ac.uk>]

Does anyone know why the first line works (below) but the second line doesn't?
and what exactly is select(0,0)? because I need an if statement to handle
this but don't know what this would be.

Anyone any ideas?


: (select( 0 , 1))  \ 1
       1
    +-----+
  1 |  0  |
  2 |  1  |
    +-----+

: (select( 0 , 0))  \ 1
                 <istmt>:  3200  conformability error
r(3200);


thanks in advance
Ade 
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