Name

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      FTHMOD

Purpose

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      Procedure to modify header information for a specified field
      in a FITS table.

Calling Sequence

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      fthmod, h, field, parameter, value
     

Input

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      h - FITS header for the table
      field - field name or number
      parameter - string name of the parameter to modify. Choices
              include:
                      TTYPE - field name
                      TUNIT - physical units for field (eg. 'ANGSTROMS')
                      TNULL - null value (string) for field, (eg. '***')
                      TFORM - format specification for the field
                      TSCAL - scale factor
                      TZERO - zero offset
              User should be aware that the validity of the change is
              not checked. Unless you really know what you are doing,
              this routine should only be used to change field names,
              units, or another user specified parameter.
      value - new value for the parameter. Refer to the FITS table
              standards documentation for valid values.

Example

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      Change the units for a field name "FLUX" to "Janskys" in a FITS table
        header,h
      IDL> FTHMOD, h, 'FLUX', 'TUNIT','Janskys'

Method

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      The header keyword <parameter> is modified
      with the new value.

History

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      version 1, D. Lindler July 1987
      Converted to IDL V5.0 W. Landsman September 1997
      Major rewrite to use new FTINFO call W. Landsman May 2000