[netcdfgroup] nc_get_vara_float on short data changes data range?

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• Subject: [netcdfgroup] nc_get_vara_float on short data changes data range?
• From: plieger <plieger@xxxxxxx>
• Date: Wed, 4 Dec 2013 16:26:42 +0100

Hi,

Here is a question about data-type conversion done by the netcdf-c library.

Is this expected behaviour? Below a small test program which illustrates this:

#include <stdio.h>
#include <netcdf.h>

int main(){
  int status;
  int ncid;
  int varid;
  static size_t start[] = {0, 0, 0};
  static size_t count[] = {1, 1, 1};
  float varData[1];
  float attrData[1];

  if (status != NC_NOERR) {return 1;}

  status = nc_inq_varid (ncid, "image1_image_data", &varid);
  if (status != NC_NOERR) {return 2;}

  status = nc_get_vara_float(ncid, varid, start, count, varData);
  if (status != NC_NOERR) {return 3;}

  status = nc_get_att_float(ncid,varid,"_FillValue",attrData);
  if (status != NC_NOERR) {return 4;}

  nc_close(ncid);

  printf("Vardata : %f\t\nAttrdata: %f\n",varData[0],attrData[0]);
  return 0;
}

it returns:
Vardata : 65535.000000
Attrdata: -1.000000

I would expect that both values are -1?

Best regards,
Maarten Plieger

--
Maarten Plieger
KNMI, R&D Information and Observation Technology, De Bilt
(t) +31 30 2206330

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  • Re: [netcdfgroup] nc_get_vara_float on short data changes data range?
    • From: Dennis Heimbigner