compositing in Grads ?

[Vincent Moron]

Hello

I am searching for info to make composites in Grads. Let say that I have a time series
T of length 360 and I would like to do composite for a 4D (lon,lat,lev,time) array with the same time
units as T. I would like for example average the anomalies of my 4D array when T is > 1 and when
it is < 1 and then make the differences. I am sure that this question has already been asked but
I cannot find the documentation. Sorry for inconvenience

Ciao

Vincent