Name

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WHERE_TAG

Purpose

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Like WHERE but works on structure tag names

Explanation

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Obtain subscripts of elements in structure array for which
a particular Tag has values in a range or matching specified values.
Like the WHERE function but for use with structures

Category

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Structures

Calling Sequence

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w = where_tag( struct, [ Nfound, TAG_NAME=, TAG_NUMBER = , RANGE =,
VALUES =, RANGE =, ISELECT =, /NOPRINT ]

Inputs

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Struct = structure array to search.

Input Keywords

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User *must* specify (1) TAG_NAME or TAG_NUMBER to search, and (2)
the VALUES or RANGE to search on
TAG_NAME = Scalar string specifying Tag Name
TAG_NUMBER = otherwise give the Tag Number,
RANGE = [min,max] range to search for in Struct,
VALUES = one or array of numbers to match for in Struct,
ISELECT= specifies indices to select only part of structure array,
(use it to recycle subscripts from previous searches).
/NOPRINT = suppress informational messages about nothing found.

Outputs

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Nfound = # of occurences found.

Result

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Function returns subscripts (indices) to desired elements.

Examples

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Suppose STR is a structure with tags CAT_NO:indgen(10), and
NAME:strarr(10). Find the indices where STR.CAT_NO is
between 3 and 5.
IDL> print, WHERE_TAG( str, TAG_NAME = 'CAT_NO', VALUE = [3,4,5] ) ;or
IDL> print, WHERE_TAG( str, TAG_NUM = 0, RANGE = [3,5])

Procedure

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Get tag number and apply the WHERE function appropriately.

Modification History

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written 1990 Frank Varosi STX @ NASA/GSFC
Stop printing "Tag <xxx> not found" with /NOPRINT, CD Pike 8-Jun-93
      Use STRJOIN for display W.L. July 2009