Add a useful package (from Source forge) for octave

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

diff --git a/octave_packages/signal-1.1.3/tukeywin.m b/octave_packages/signal-1.1.3/tukeywin.m
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+## Copyright (C) 2007 Laurent Mazet <mazet@crm.mot.com>
+##
+## 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{w} =} tukeywin (@var{L}, @var{r})
+## Return the filter coefficients of a Tukey window (also known as the
+## cosine-tapered window) of length @var{L}. @var{r} defines the ratio
+## between the constant section and and the cosine section. It has to be
+## between 0 and 1. The function returns a Hanning window for @var{r}
+## egals 0 and a full box for @var{r} egals 1. By default @var{r} is set
+## to 1/2.
+##
+## For a definition of the Tukey window, see e.g. Fredric J. Harris,
+## "On the Use of Windows for Harmonic Analysis with the Discrete Fourier
+## Transform, Proceedings of the IEEE", Vol. 66, No. 1, January 1978,
+## Page 67, Equation 38.
+## @end deftypefn
+
+function w = tukeywin (L, r = 1/2)
+
+  if (nargin < 1 || nargin > 2)
+    print_usage;
+  elseif (nargin == 2)
+      ## check that 0 < r < 1
+      if r > 1
+        r = 1;
+      elseif r < 0
+        r = 0;
+      endif
+  endif
+
+  ## generate window
+  switch r
+    case 0,
+      ## full box
+      w = ones (L, 1);
+    case 1,
+      ## Hanning window
+      w = hanning (L);
+    otherwise
+      ## cosine-tapered window
+      t = linspace(0,1,L)(1:end/2)';
+      w = (1 + cos(pi*(2*t/r-1)))/2;
+      w(floor(r*(L-1)/2)+2:end) = 1;
+      w = [w; ones(mod(L,2)); flipud(w)];
+  endswitch
+
+endfunction
+
+%!demo
+%! L = 100;
+%! r = 1/3;
+%! w = tukeywin (L, r);
+%! title(sprintf("%d-point Tukey window, R = %d/%d", L, [p, q] = rat(r), q));
+%! plot(w);