How to check the existence of a mata object?

[Chi-lin Tsai]

Hello,

I wonder whether there is a Mata command for checking the existence of a Mata object.
In Stata, we can use confirm and _rc. Can we do the same thing in Mata?

Thank you very much.

[Christophe Kolodziejczyk]

see mata function findexternal()

http://www.stata.com/help.cgi?mf_findexternal

[Chi-lin Tsai]

Kolodziejczyk, thanks for pointing out findexternal. I had misunderstood that command. I thought it was for checking Stata's global objects. Now I realise that findexternal does allow for checking the existence of Mata objects. Below is a toy example:

. mata: mata drop *
. mata: A=J(1,2,3)

. mata: findexternal("A") != J(1,1,NULL)
 1

. mata: findexternal("B") != J(1,1,NULL)
 0

Thanks a lot.