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      Contract a vector or up to 25 vectors by removing specified elements

Calling Sequence

      REMOVE, index, v1,[ v2, v3, v4, v5, v6, ... v25]


      INDEX - scalar or vector giving the index number of elements to
              be removed from vectors. Duplicate entries in index are
              ignored. An error will occur if one attempts to remove
              all the elements of a vector. REMOVE will return quietly
              (no error message) if index is !NULL or undefined.


      v1 - Vector or array. Elements specifed by INDEX will be
              removed from v1. Upon return v1 will contain
              N fewer elements, where N is the number of distinct values in
      v2,v3,...v25 - additional vectors containing
              the same number of elements as v1. These will be
              contracted in the same manner as v1.


      (1) If INDEX = [2,4,6,4] and V = [1,3,4,3,2,5,7,3] then after the call
              IDL> remove,index,v
      V will contain the values [1,3,3,5,3]
      (2) Suppose one has a wavelength vector W, and three associated flux
      vectors F1, F2, and F3. Remove all points where a quality vector,
      EPS is negative
              IDL> bad = where( EPS LT 0, Nbad)
              IDL> if Nbad GT 0 then remove, bad, w, f1, f2, f3


      If more than one element is to be removed, then HISTOGRAM is used
      to generate a 'keep' subscripting vector. To minimize the length of
      the subscripting vector, it is only computed between the minimum and
      maximum values of the index. Therefore, the slowest case of REMOVE
      is when both the first and last element are removed.

Revision History

      Written W. Landsman ST Systems Co. April 28, 1988
      Cleaned up code W. Landsman September, 1992
      Major rewrite for improved speed W. Landsman April 2000
      Accept up to 25 variables, use SCOPE_VARFETCH internally
              W. Landsman Feb 2010
      Fix occasional integer overflow problem V. Geers Feb 2011
      Quietly return if index is !null or undefined W.L. Aug 2011

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