The module "mat2groups" of the Mastrave modelling library

Copyright and license notice of the function mat2groups

Copyright © 2005,2006,2007,2008,2009,2010,2011 Daniele de Rigo

The file mat2groups.m is part of Mastrave.

Mastrave is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

Mastrave is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

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Function declaration

groups = mat2groups( matrix                   ,
                     groups_length            ,
                     mode          = '--none' )

Description

Returns a sparse matrix groups whose nonzeros elements are the elements of the input argument matrix . groups has an amount of columns equal to the number of elements of the vector of non-negative integers groups_length . Each column of groups has an amount of rows equal to the corresponding element of groups_length . Depending on the value of mode , the elements of each groups column may be in the same order of the corresponding elements of matrix (default behaviour), or may be ordered in ascending or descending order.

Input arguments

 matrix            ::numeric::
                   Matrix of numbers.

 groups_length     ::natural::
                   Vector containing the desired length of each group in
                   which  matrix  has to be splitted.

 mode              ::string::
                   Direction in which each column of the cell-array  groups 
                   will be sorted. Valid modes are:

                        mode     │      meaning
                   ──────────────┼───────────────────────────────────────
                     'none'      │ Leave the elements of  groups  in
                     '--none'    │ the same order of those of  matrix :
                     (default)   │ nonzeros( groups ) ==  matrix (:) .
                   ──────────────┼───────────────────────────────────────
                     'ascend'    │ Sort in  ascending order.
                     '--ascend'  │
                   ──────────────┼───────────────────────────────────────
                     'descend'   │ Sort in descending order.
                     '--descend' │

Example of usage

   % Basic conversion
   n_elems = [2 0 3 4 0 0 5 3 ]
   data    = randn( 1, sum(n_elems) )
   sp_data = mat2groups( data, n_elems );
   full( sp_data )
   all( nonzeros(sp_data) == data(:) )

   % Adding sort for no-empty elements
   sp_data = mat2groups( data, n_elems, '--descend' );
   full( sp_data )
   sp_data = mat2groups( data, n_elems, '--ascend' );
   full( sp_data )

   % Difference between  mat2groups  and  score
   [rev_id, sorted_data, sort_id] = score( sp_data , '--ascend' );
   full( sorted_data )

See also:
   mat2multi, multi2mat



Keywords:
   matrices, sparse matrices



Version: 0.5.1

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