defining new variable

[L Wu]

Hi, all, I have a question about defining new variables in grads.

I have variable temp(96,80,14), if I want to define new variable like
1000-day average of zonal mean temperature, and then plot the new variable,
I did it this way:

define tz=ave(temp,x=1,x=96)
set fwrite tz.dat
set gxout fwrite
define tmean=ave(tz, t=1,t=1000)
set fwrite tmean.dat
set gxout fwrite
set cint 5
set clab forced
set clskip 2
d tmean

but I cannot get the right plot, can anybody help me to see where is wrong,
and whether need I to use set fwrite... and set gxout fwrite twice?

Thanks in advance!