[gradsusr] Temporal correlation

[Ismaila Diallo]

Dear,

i've two variable covering the same period and i try to calculate the temporal 
correlation between them by this Tcorr but i get some error.

Here are my script:

set vrange 0 80
set dfile 1
set lon -17.5
set lat 14.73
set t 151 273
set tlsupp year
set rgb 19 0 60 0
set ccolor 19
set cmark 0
set line 2
define aa=rt.1
d aa

set dfile 2
set lon -17.5
set lat 14.73
set cmark 1
set line 1
set rgb 20 0 150 0
set ccolor 20

define bb=rt.2
d bb


set t 151
define r1=tcorr(aa,bb,t=151,t=273)
d r1

the script work until tcorr and there i get this error:

define r1=tcorr(aa,bb,t=151,t=273)
TCORR:  dim = 3, start = 151, end = 273
Data Request Error: Invalid grid coordinates
  World coordinates convert to non-integer  grid coordinates
    Variable = aa  Dimension = 3 
Error from TCORR:  Error getting grids
Operation Error:  Error from tcorr function
  Error ocurred at column 1
DEFINE error:  Invalid expression. 
EXEC error:  error in atrib_station2005.  EXEC stopped.

all comment and help are welcome.

Sincerely
ismaila