# coyote: CGRANDOMINDICES

- coyote/Utilities
- [Source code]

Description

      This function returns random indices without replacement. You can, for example,
      select 100 random, unique indices from a vector of 10000 random indices.
      The program uses an `algorithm offered by JD Smith <http://www.idlcoyote.com/code_tips/randomindex.html>`
      on the IDL newsgroup.

Categories

      Utilities

Params

      length: in, required, type=long
         The number of random values to be considered in the selection process. In
         other words, the length of the selection vector.
      number: in, required, type=long
         The number of unique, random indices you want the function to return out of
         the selection vector.

Keywords

      seed: in, optional, type=long
         The seed for the random number generator, RandomU. This is also an output
         variable, which you should use as the input to the next cgRandomIndices call,
         if you need to do several random selections very quickly in a program.

Examples

      To select 10 random indices from a list of 100::
         indices = cgRandomIndices(100, 10, SEED=seed)
         Print, indices
              7  13  20  21  32  44  50  66  80  93

Author

      FANNING SOFTWARE CONSULTING::
          David W. Fanning
          1645 Sheely Drive
          Fort Collins, CO 80526 USA
          Phone: 970-221-0438
          E-mail: david@idlcoyote.com
          Coyote's Guide to IDL Programming: http://www.idlcoyote.com

History

      Change History::
         Written, 22 December 2011 from an algorithm by JD Smith. David W. Fanning.

Copyright

      Copyright (c) 2011, Fanning Software Consulting, Inc.