Re: warning:NetOpenFile

From: Mary Haley <haley_at_nyahnyahspammersnyahnyah>
Date: Mon Oct 24 2011 - 09:00:48 MDT

Dear Ivanna,

This warning is likely occuring because your data variable is one type (say float), but your "missing_value" attribute is a higher type (say double).

When NCL sees a "missing_value" attribute and not a "_FillValue" attribute, it tries to create a "_FillValue" attribute for you, based on "missing_value". If "missing_value" is a higher type than your data, then it can't safely be coerced to the lower type, and you get a warning.

You can get rid of this warning by adding the following line before your "addfile" statement:


Really, the best thing to do is to find out why "missing_value" is a higher type than your data, and try to fix this.

Here's a code snippet that creates a dummy file with float data and double "missing_value" attribute.
You'll see the warning the first time you open the file for reading.

This code then fixes the "missing_value" to be a float, and the warning goes away:

;---Generate some dummy float data with a double "missing_value"
  x = random_uniform(0,100,(/10,20/))
  x@missing_value = 1d20

;---Write array to NetCDF file
  filename = ""
  if(isfilepresent(filename)) then
    system("/bin/rm " + filename)
  end if
  fout = addfile(filename,"c")
  fout->x = x

; setfileoption("nc","MissingToFillValue",False)

;---Simply opening the file will generate a warning
  fin = addfile(filename,"w") ; open for reading and writing
  xin = fin->x

  print(" typeof(xin@missing_value) = " + typeof(xin@missing_value))

;---Fix the "missing_value" on the file to be a "float"
  missing_value = tofloat(xin@missing_value)
  fin->x@missing_value = missing_value

;---Close the file

; Reopen the file. Note there's no warning this time, and
; this time a _FillValue attribute is added
  fin = addfile(filename,"r")
  xin = fin->x

  print(" typeof(xin@missing_value) = " + typeof(xin@missing_value))


On Oct 23, 2011, at 11:24 PM, Ivanna Mo wrote:

> Hi,
> When I run my ncl script, I got a warning:NetOpenFile: MissingToFillValue option set True, but missing_value attribute and data variable (air) types differ: not adding virtual _FillValue attribute
> I wonder how can I eliminate this warning.
> Thanks in advance.
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Received on Mon Oct 24 09:00:59 2011

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