open 2 files in grads

[hossein lotfi]

Hi all user
I want to open 2 files in grads and display variables
can any one help me for errors shown below;

ga-> 'set dfile 2'
Default file set to: model_25.grb2
ga-> 'define r=rhprs'
  Warning issued for variable = rhprs
Define memory allocation size = 84680 bytes
Cannot contour grid - all undefined values

 and;

'set dfile 2'
 'Default file set to: model_25.grb2'
'ga-> 'd rhprs'
Data Request Error: Invalid grid coordinates
  World coordinates convert to non-integer  grid coordinates
    Variable = rhprs  Dimension = 2
  Error ocurred at column 1
DISPLAY error:  Invalid expression
  Expression = rhprs

thanks
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