Scatter diagram

[Boyin Huang]

Can grads draw scatter diagram using 4-D data?

Assuming I have T(x,y,z,t) and S(x,y,z,t)

If I fix z and t,
set x 1 10
set y 1 10
set t 1
set z 1
I can draw the scatter diagram using 'd t; s'

What I want is
set x 1 10
set y 1 10
set t 1 10
set z 1 10
'd t;s'

but grads prompts
Operation error:  Invalid dimension environment
  Looping dimension does not vary

Any suggestions? Thanks.