1、不同的文件進行不同的設置：'set dfile 2'
2、讀取不同文件的變量：qv.2
實例如下：
'reinit'
'open e:\tskt.CTL'
'open e:\uwnd.CTL'
'open e:\qv.CTL'
'set parea 2.50 8.50 3.00 8.00'
'enable print e:/pingjun.gmf'
'set grads off'
'set grid off'
'set dfile 1'
'set z 1'
'set t 1'
'set lon 60 150'
'set lat 0 50'
'set gxout shaded'
'set rgb 16 175 175 175'
'set clevs -2.101 2.101'
'set ccols 16 0 16'
'd ttest'
*'cbarn 0.8 1 8.65 5.7'
'close 1'
*填色圖是檢驗圖
'set dfile 2'
'set x 1'
'set y 1'
'set z 1'
'set t 1 10'
'define u=uwnd'
'set dfile 3'
'set lon 60 150'
'set lat 0 50'
'set z 1'
'set t 1'
'set gxout contour'
'd tcorr(u,qv.3,t=1,t=10)'
*等值線圖是時間序列與場相關圖
'print'
'disable print'
'reinit'
;
DSET E:\tskt.grd
UNDEF -9.96921E+36
TITLE daily means ttst from the NCEP Reanalysis
XDEF 144 LINEAR 0 2.5
YDEF 73 LINEAR -90 2.5
ZDEF 1 LINEAR 0 1
TDEF 1 LINEAR 00Z01JAN1983 1dy
VARS 1
ttest 1 99 t-test dataset
ENDVARS
DSET E:\qv.grd
undef -9.96921E+36
TITLE daly means q1 from the NCEP Reanalysis
XDEF 144 LINEAR 0 2.5
YDEF 73 LINEAR -90 2.5
ZDEF 1 LINEAR 0 1
TDEF 10 LINEAR 00Z01JAN1983 1dy
VARS 1
qv 1 99 qv dataset
ENDVARS
DSET E:\a.grd
undef -9.96921E+36
TITLE daly means uwnd from the NCEP Reanalysis
XDEF 1 LINEAR 0 1
YDEF 1 LINEAR 0 1
ZDEF 1 LINEAR 0 1
TDEF 10 LINEAR 00Z01JAN1983 1dy
VARS 1
uwnd 1 99 u dataset
ENDVARS