Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / signal-1.1.3 / xcorr2.m

diff --git a/octave_packages/signal-1.1.3/xcorr2.m b/octave_packages/signal-1.1.3/xcorr2.m
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+## Copyright (C) 2000 Dave Cogdell <cogdelld@asme.org>
+## Copyright (C) 2000 Paul Kienzle <pkienzle@users.sf.net>
+##
+## 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{c} =} xcorr2 (@var{a})
+## @deftypefnx {Function File} {@var{c} =} xcorr2 (@var{a}, @var{b})
+## @deftypefnx {Function File} {@var{c} =} xcorr2 (@dots{}, @var{scale})
+## Compute the 2D cross-correlation of matrices @var{a} and @var{b}.
+##
+## If @var{b} is not specified, it defaults to the same matrix as @var{a}, i.e.,
+## it's the same as @code{xcorr(@var{a}, @var{a})}.
+##
+## The optional argument @var{scale}, defines the type of scaling applied to the
+## cross-correlation matrix (defaults to "none"). Possible values are:
+## @itemize @bullet
+## @item "biased"
+##
+## Scales the raw cross-correlation by the maximum number of elements of @var{a}
+## and @var{b} involved in the generation of any element of @var{c}.
+##
+## @item "unbiased"
+##
+## Scales the raw correlation by dividing each element in the cross-correlation
+## matrix by the number of products @var{a} and @var{b} used to generate that
+## element 
+##
+## @item "coeff"
+##
+## Normalizes the sequence so that the largest cross-correlation element is
+## identically 1.0.
+##
+## @item "none"
+##
+## No scaling (this is the default).
+## @end itemize
+## @seealso{conv2, corr2, xcorr}
+## @end deftypefn
+
+function c = xcorr2 (a, b = a, biasflag = "none")
+
+  if (nargin < 1 || nargin > 3)
+    print_usage;
+  elseif (nargin == 2 && ischar (b))
+    biasflag = b;
+    b        = a;
+  endif
+
+  ## compute correlation
+  [ma,na] = size(a);
+  [mb,nb] = size(b);
+  c = conv2 (a, conj (b (mb:-1:1, nb:-1:1)));
+
+  ## bias routines by Dave Cogdell (cogdelld@asme.org)
+  ## optimized by Paul Kienzle (pkienzle@users.sf.net)
+  if strcmp(lower(biasflag), 'biased'),
+    c = c / ( min ([ma, mb]) * min ([na, nb]) );
+  elseif strcmp(lower(biasflag), 'unbiased'), 
+    lo   = min ([na,nb]);
+    hi   = max ([na, nb]);
+    row  = [ 1:(lo-1), lo*ones(1,hi-lo+1), (lo-1):-1:1 ];
+
+    lo   = min ([ma,mb]);
+    hi   = max ([ma, mb]);
+    col  = [ 1:(lo-1), lo*ones(1,hi-lo+1), (lo-1):-1:1 ]';
+
+    bias = col*row;
+    c    = c./bias;
+
+  elseif strcmp(lower(biasflag),'coeff'),
+    c = c/max(c(:))';
+  else
+    error ("invalid type of scale %s", biasflag);
+  endif
+endfunction