简单数据处理的问题

求实求是

1、缺省值设置问题
fatal:Type Mismatch: The type of missing value could not be converted to type of variable (ndvi)
fatal:["Execute.c":8637]:Execute: Error occurred at or near line 31 in file data_ana.ncl

2、用short2flt将短型数据转换为浮点型数据
warning:stringtofloat: a bad value was passed; input strings must contain numeric digits, replacing with missing value
fatal:The result of the conditional expression yields a missing value. NCL can not determine branch, see ismissing function
fatal:["Execute.c":8637]:Execute: Error occurred at or near line 2014 in file $NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl
下面是部分代码：
      ndvi3g_geo_v1_fi = addfile(fils(k),"r")
      ndvi            := ndvi3g_geo_v1_fi->ndvi     ;type short
      printVarSummary(ndvi)
      ndvi@_FillValue  =ndvi@missing_value            ;???
      ndvi            :=short2flt(ndvi)
      
刚开始处理数据，这些个问题已经困扰我不少时间