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1 ## Copyright (C) 2004 Paul Kienzle |
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2 ## |
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3 ## This program is free software and is in the public domain |
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4 |
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5 ## -*- texinfo -*- |
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6 ## @deftypefn {Function File} {[@var{count}, @var{mean}, @var{var}] =} spstats (@var{s}) |
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7 ## @deftypefnx {Function File} {[@var{count}, @var{mean}, @var{var}] =} spstats (@var{s}, @var{j}) |
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8 ## Return the stats for the non-zero elements of the sparse matrix @var{s}. |
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9 ## @var{count} is the number of non-zeros in each column, @var{mean} |
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10 ## is the mean of the non-zeros in each column, and @var{var} is the |
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11 ## variance of the non-zeros in each column. |
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12 ## |
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13 ## Called with two input arguments, if @var{s} is the data and @var{j} |
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14 ## is the bin number for the data, compute the stats for each bin. In |
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15 ## this case, bins can contain data values of zero, whereas with |
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16 ## @code{spstats (@var{s})} the zeros may disappear. |
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17 ## @end deftypefn |
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18 |
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19 function [count, mean, var] = spstats (S, j) |
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20 |
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21 if (nargin < 1 || nargin > 2) |
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22 print_usage (); |
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23 endif |
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24 |
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25 if (nargin == 1) |
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26 [i, j, v] = find (S); |
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27 else |
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28 v = S; |
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29 i = 1:length (v); |
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30 S = sparse (i, j, v); |
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31 endif |
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32 [n, m] = size (S); |
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33 |
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34 count = spsum (sparse (i, j, 1, n, m)); |
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35 if (nargout > 1) |
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36 mean = spsum (S) ./ count; |
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37 end |
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38 if (nargout > 2) |
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39 ## FIXME Variance with count = 0 or 1? |
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40 diff = S - sparse (i, j, mean(j), n, m); |
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41 var = spsum (diff .* diff) ./ (count - 1); |
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42 end |
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43 endfunction |
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44 |
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45 %!test |
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46 %! [n,m,v] = spstats([1 2 1 2 3 4],[2 2 1 1 1 1]); |
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47 %! assert(n,[4,2]); |
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48 %! assert(m,[10/4,3/2],10*eps); |
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49 %! assert(v,[5/3,1/2],10*eps); |
