Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / communications-1.1.1 / quantiz.m

diff --git a/octave_packages/communications-1.1.1/quantiz.m b/octave_packages/communications-1.1.1/quantiz.m
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+## Copyright (C) 2001 Paul Kienzle
+##
+## 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{qidx} = } quantiz (@var{x}, @var{table})
+## @deftypefnx {Function File} {[@var{qidx}, @var{q}] = } quantiz (@var{x}, @var{table}, @var{codes})
+## @deftypefnx {Function File} {[ @var{qidx}, @var{q}, @var{d}] = } quantiz (@var{...})
+##
+## Quantization of an arbitrary signal relative to a paritioning.
+##
+## @table @code
+## @item qidx = quantiz(x, table)
+##   Determine position of x in strictly monotonic table.  The first
+##   interval, using index 0, corresponds to x <= table(1).
+##   Subsequent intervals are table(i-1) < x <= table(i).
+##
+## @item [qidx, q] = quantiz(x, table, codes)
+##   Associate each interval of the table with a code.  Use codes(1) 
+##   for x <= table(1) and codes(n+1) for table(n) < x <= table(n+1).
+##
+## @item [qidx, q, d] = quantiz(...)
+##   Compute distortion as mean squared distance of x from the
+##   corresponding quantization values.
+## @end table
+## @end deftypefn
+
+function [qidx, q, d] = quantiz (x, table, codes)
+  if (nargin < 2 || nargin > 3)
+    usage("[qidx, q, d] = quantiz(x, table, codes)");
+  endif
+
+  qidx = length(table) - lookup(flipud(table(:)), x(:));
+  if (nargin > 2 && nargout > 1)
+    q = codes(qidx + 1);
+  endif
+  if (nargout > 2)
+    table = [table(1) ; table(:) ];
+    d = sumsq (x(:) - q(:)) / length(x);
+  endif
+endfunction