Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / statistics-1.1.3 / squareform.m

diff --git a/octave_packages/statistics-1.1.3/squareform.m b/octave_packages/statistics-1.1.3/squareform.m
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+## Copyright (C) 2006, 2008 Bill Denney <bill@denney.ws>
+##
+## This program 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.
+##
+## This program 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
+## this program; if not, see <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {@var{y} =} squareform (@var{x})
+## @deftypefnx {Function File} {@var{y} =} squareform (@var{x}, @
+## "tovector")
+## @deftypefnx {Function File} {@var{y} =} squareform (@var{x}, @
+## "tomatrix")
+## Convert a vector from the pdist function into a square matrix or from
+## a square matrix back to the vector form.
+##
+## The second argument is used to specify the output type in case there
+## is a single element.
+## @seealso{pdist}
+## @end deftypefn
+
+## Author: Bill Denney <bill@denney.ws>
+
+function y = squareform (x, method)
+
+  if nargin < 1
+    print_usage ();
+  elseif nargin < 2
+    if isscalar (x) || isvector (x)
+      method = "tomatrix";
+    elseif issquare (x)
+      method = "tovector";
+    else
+      error ("squareform: cannot deal with a nonsquare, nonvector \
+       input");
+    endif
+  endif
+  method = lower (method);
+
+  if ! strcmp ({"tovector" "tomatrix"}, method)
+    error ("squareform: method must be either \"tovector\" or \
+       \"tomatrix\"");
+  endif
+
+  if strcmp ("tovector", method)
+    if ! issquare (x)
+      error ("squareform: x is not a square matrix");
+    endif
+
+    sx = size (x, 1);
+    y = zeros ((sx-1)*sx/2, 1);
+    idx = 1;
+    for i = 2:sx
+      newidx = idx + sx - i;
+      y(idx:newidx) = x(i:sx,i-1);
+      idx = newidx + 1;
+    endfor
+  else
+    ## we're converting to a matrix
+
+    ## make sure that x is a column
+    x = x(:);
+
+    ## the dimensions of y are the solution to the quadratic formula
+    ## for:
+    ## length(x) = (sy-1)*(sy/2)
+    sy = (1 + sqrt (1+ 8*length (x)))/2;
+    y = zeros (sy);
+    for i = 1:sy-1
+      step = sy - i;
+      y((sy-step+1):sy,i) = x(1:step);
+      x(1:step) = [];
+    endfor
+    y = y + y';
+  endif
+
+endfunction
+
+## make sure that it can go both directions automatically
+%!assert(squareform(1:6), [0 1 2 3;1 0 4 5;2 4 0 6;3 5 6 0])
+%!assert(squareform([0 1 2 3;1 0 4 5;2 4 0 6;3 5 6 0]), [1:6]')
+
+## make sure that the command arguments force the correct behavior
+%!assert(squareform(1), [0 1;1 0])
+%!assert(squareform(1, "tomatrix"), [0 1;1 0])
+%!assert(squareform(1, "tovector"), zeros(0,1))