What is mean by True or False in mask function.?

What is mean by True or False in mask function...When I read the document it
make me confused...
The following example given in document confused me...

The following line mask *a* at locations where ma0 is not-equal-to 2
 out1 = *mask*( a, (ma0.ne.2), True)

In my case I want to mask *aveX_u* and *aveX_v* at locations where both *
alpha_u* and *alpha_v* less than or equal to 95..So as per the above example
I used the following line.

aveX_u = mask(aveX_u,( alpha_u.le.95.and.alpha_v.le.95),True)
aveX_v = mask(aveX_v, (alpha_u.le.95.and.alpha_v.le.95),True)

But I am not getting the desired result..If I set True to False (as given
below) I think I am getting the correct values...

aveX_u = mask(aveX_u,( alpha_u.le.95.and.alpha_v.le.95),False)
aveX_v = mask(aveX_v, (alpha_u.le.95.and.alpha_v.le.95),False)

So anyone can give more information on True/False
Also which one is correct in my case..

Thanks in advance...

-- 
**********************************
Sabeerali
Climate and Global Modeling Division
Indian Institute of Tropical Meteorology
Pashan, Pune, 411 008
****************************************

_______________________________________________
ncl-talk mailing list
List instructions, subscriber options, unsubscribe:
http://mailman.ucar.edu/mailman/listinfo/ncl-talk
Received on Wed Apr 21 23:03:33 2010