update packages

[CreaPhase.git] / octave_packages / m / sparse / spstats.m

diff --git a/octave_packages/m/sparse/spstats.m b/octave_packages/m/sparse/spstats.m
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+## Copyright (C) 2004-2012 Paul Kienzle
+##
+## This file is part of Octave.
+##
+## Octave 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.
+##
+## Octave 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.
+##
+## You should have received a copy of the GNU General Public License
+## along with Octave; see the file COPYING.  If not, see
+## <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn  {Function File} {[@var{count}, @var{mean}, @var{var}] =} spstats (@var{S})
+## @deftypefnx {Function File} {[@var{count}, @var{mean}, @var{var}] =} spstats (@var{S}, @var{j})
+## Return the stats for the non-zero elements of the sparse matrix @var{S}.
+## @var{count} is the number of non-zeros in each column, @var{mean}
+## is the mean of the non-zeros in each column, and @var{var} is the
+## variance of the non-zeros in each column.
+##
+## Called with two input arguments, if @var{S} is the data and @var{j}
+## is the bin number for the data, compute the stats for each bin.  In
+## this case, bins can contain data values of zero, whereas with
+## @code{spstats (@var{S})} the zeros may disappear.
+## @end deftypefn
+
+function [count, mean, var] = spstats (S, j)
+
+  if (nargin < 1 || nargin > 2)
+    print_usage ();
+  endif
+
+  if (nargin == 1)
+    [i, j, v] = find (S);
+  else
+    v = S;
+    i = 1:length (v);
+    S = sparse (i, j, v);
+  endif
+  [n, m] = size (S);
+
+  count = sum (sparse (i, j, 1, n, m));
+  if (nargout > 1)
+    mean = sum (S) ./ count;
+  endif
+  if (nargout > 2)
+    ## FIXME Variance with count = 0 or 1?
+    diff = S - sparse (i, j, mean(j), n, m);
+    var = sum (diff .* diff) ./ (count - 1);
+  endif
+
+endfunction
+
+
+%!test
+%! [n,m,v] = spstats([1 2 1 2 3 4],[2 2 1 1 1 1]);
+%! assert(n,sparse([4,2]));
+%! assert(m,sparse([10/4,3/2]),10*eps);
+%! assert(v,sparse([5/3,1/2]),10*eps);