Welcome to the Harris Geospatial product documentation center. Here you will find reference guides, help documents, and product libraries.


  >  Docs Center  >  Libraries  >  ASTROLIB  >  WHERENAN

WHERENAN

WHERENAN

Name


      WHERENAN()

Purpose


      Find the indices of all big-endian NaN values in an array. OBSOLETE

Explanation


      Find the positions of all values within an array that correspond to the
      big-endian NaN (not-a-number) special values.
      THIS PROCEDURE ONLY IDENTIFIES BIG_ENDIAN NaN VALUES. DO NOT USE IT
      TO IDENTIFY NaN VALUES IN GENERAL. Instead, to identify NaN values on
      the host machine use the FINITE() function
      IDL> result = where( finite(array,/NAN) )
     
      The main purpose of this routine is to catch NaN special values
      written in big_endian format (e.g. FITS data) on a little endian
      machine prior to conversion with e.g. IEEE_TO_HOST. It was needed
      many years ago because VMS machines could not handle big-endian
      special values, but this routine is now kept only for backwards
      compatibility.

Calling Sequence


      Result = WHERENAN( ARRAY [, COUNT ] )

Input Parameters


      ARRAY = Array to test against the IEEE NaN special values. Must be
                of either floating point, double-precision, or complex type.

Outputs


      The result of the function is the indices of all values of ARRAY
      corresponding to the IEEE NaN specification, similar to the IDL WHERE
      function.

Optional Output Parameters


      COUNT = Number of values found corresponding to IEEE NaN.

Side Effects


      If no NaN values are found, or if ARRAY is not of type float, double
      precision, or complex, then -1 is returned, and COUNT is set to 0.

Restrictions


      ARRAY must be of type float, double-precision, or complex.

Procedure


      The bit patterns of the numbers being tested are compared against the
      IEEE NaN standard.

Modification History


      William Thompson, Feb. 1992.
      William Thompson, Oct. 1992, fixed bug regarding order of bytes on VAX
              machines.
      Converted to IDL V5.0 W. Landsman September 1997



© 2018 Harris Geospatial Solutions, Inc. |  Legal
My Account    |    Store    |    Contact Us