用scorr画图出现问题

hgsndg

'reinit'
'sdfopen E:\aa\uwnd.1987.nc'
'set dfile 1'
'set lat 0 10'
'set lon 100 130'
'set lev 850'
'define u850=uwnd'
'set lev 200'
'define u200=uwnd'
'define udif=u200-u850'
'sdfopen E:\aa\vwnd.1987.nc'
'set dfile 2'
'set lat 0 10'
'set lon 100 130'
'set lev 200'
'define v200=vwnd'
'set lat 0 10'
'set lon 100 130'
'set z 1'
'set t 1'
'define r=tcorr(udif,v200,t=160,t=190)'
'set xlopts -1 1 0.15'
'set ylopts -1 1 0.15'
'set gxout shaded'
'd r'
;
报错内容为：
Error from TCORR:  1st arg must be 0-D
Error from TCORR:  Error getting grids
Operation Error:  Error from tcorr function
  Error ocurred at column 1
DEFINE error:  Invalid expression.
Syntax Error:  Invalid Operand
  'r' not a variable or function name
  Error ocurred at column 1
DISPLAY error:  Invalid expression
  Expression = r

有大神知道为什么吗？谢谢啦