Add a useful package (from Source forge) for octave

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

diff --git a/octave_packages/signal-1.1.3/kaiser.m b/octave_packages/signal-1.1.3/kaiser.m
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+## Copyright (C) 1995, 1996, 1997 Kurt Hornik <Kurt.Hornik@ci.tuwien.ac.at>
+## 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/>.
+
+## usage:  kaiser (L, beta)
+##
+## Returns the filter coefficients of the L-point Kaiser window with
+## parameter beta.
+##
+## For the definition of the Kaiser window, see A. V. Oppenheim &
+## R. W. Schafer, "Discrete-Time Signal Processing".
+##
+## The continuous version of width L centered about x=0 is:
+##
+##         besseli(0, beta * sqrt(1-(2*x/L).^2))
+## k(x) =  -------------------------------------,  L/2 <= x <= L/2
+##                besseli(0, beta)
+##
+## See also: kaiserord
+
+function w = kaiser (L, beta = 0.5)
+
+  if (nargin < 1)
+    print_usage;
+  elseif !(isscalar (L) && (L == round (L)) && (L > 0))
+    error ("kaiser:  L has to be a positive integer");
+  elseif !(isscalar (beta) && (beta == real (beta)))
+    error ("kaiser:  beta has to be a real scalar");
+  endif
+  
+  if (L == 1)
+    w = 1;
+  else
+    m = L - 1;
+    k = (0 : m)';
+    k = 2 * beta / m * sqrt (k .* (m - k));
+    w = besseli (0, k) / besseli (0, beta);
+  endif
+
+endfunction
+
+%!demo
+%! % use demo("kaiserord");