1 ## Copyright (C) 2004-2012 Paul Kienzle
3 ## This file is part of Octave.
5 ## Octave is free software; you can redistribute it and/or modify it
6 ## under the terms of the GNU General Public License as published by
7 ## the Free Software Foundation; either version 3 of the License, or (at
8 ## your option) any later version.
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13 ## General Public License for more details.
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20 ## @deftypefn {Function File} {[@var{count}, @var{mean}, @var{var}] =} spstats (@var{S})
21 ## @deftypefnx {Function File} {[@var{count}, @var{mean}, @var{var}] =} spstats (@var{S}, @var{j})
22 ## Return the stats for the non-zero elements of the sparse matrix @var{S}.
23 ## @var{count} is the number of non-zeros in each column, @var{mean}
24 ## is the mean of the non-zeros in each column, and @var{var} is the
25 ## variance of the non-zeros in each column.
27 ## Called with two input arguments, if @var{S} is the data and @var{j}
28 ## is the bin number for the data, compute the stats for each bin. In
29 ## this case, bins can contain data values of zero, whereas with
30 ## @code{spstats (@var{S})} the zeros may disappear.
33 function [count, mean, var] = spstats (S, j)
35 if (nargin < 1 || nargin > 2)
48 count = sum (sparse (i, j, 1, n, m));
50 mean = sum (S) ./ count;
53 ## FIXME Variance with count = 0 or 1?
54 diff = S - sparse (i, j, mean(j), n, m);
55 var = sum (diff .* diff) ./ (count - 1);
62 %! [n,m,v] = spstats([1 2 1 2 3 4],[2 2 1 1 1 1]);
63 %! assert(n,sparse([4,2]));
64 %! assert(m,sparse([10/4,3/2]),10*eps);
65 %! assert(v,sparse([5/3,1/2]),10*eps);