Add a useful package (from Source forge) for octave

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

diff --git a/octave_packages/signal-1.1.3/triang.m b/octave_packages/signal-1.1.3/triang.m
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+## Copyright (C) 2000-2002 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:  w = triang (L)
+##
+## Returns the filter coefficients of a triangular window of length L.
+## Unlike the bartlett window, triang does not go to zero at the edges
+## of the window.  For odd L, triang(L) is equal to bartlett(L+2) except
+## for the zeros at the edges of the window.
+
+function w = triang(L)
+  if (nargin != 1)
+    print_usage;
+  elseif (!isscalar(L) || L != fix (L) || L < 1)
+    error("triang: L has to be an integer > 0");
+  endif
+  w = 1 - abs ([-(L-1):2:(L-1)]' / (L+rem(L,2)));
+endfunction
+
+%!error triang
+%!error triang(1,2)
+%!error triang([1,2]);
+%!assert (triang(1), 1)
+%!assert (triang(2), [1; 1]/2)
+%!assert (triang(3), [1; 2; 1]/2);
+%!assert (triang(4), [1; 3; 3; 1]/4);
+%!test
+%! x = bartlett(5);
+%! assert (triang(3), x(2:4));
+
+%!demo
+%! subplot(221); axis([-1, 1, 0, 1.3]); grid("on");
+%! title("comparison with continuous for odd n");
+%! n=7; k=(n-1)/2; t=[-k:0.1:k]/(k+1);
+%! plot(t,1-abs(t),";continuous;",[-k:k]/(k+1),triang(n),"g*;discrete;");
+%!
+%! subplot(222); axis([-1, 1, 0, 1.3]); grid("on");
+%! n=8; k=(n-1)/2; t=[-k:0.1:k]/(k+1/2);
+%! title("note the higher peak for even n");
+%! plot(t,1+1/n-abs(t),";continuous;",[-k:k]/(k+1/2),triang(n),"g*;discrete;");
+%!
+%! subplot(223); axis; grid("off");
+%! title("n odd, triang(n)==bartlett(n+2)");
+%! n=7;
+%! plot(0:n+1,bartlett(n+2),"g-*;bartlett;",triang(n),"r-+;triang;");
+%!
+%! subplot(224); axis; grid("off");
+%! title("n even, triang(n)!=bartlett(n+2)");
+%! n=8;
+%! plot(0:n+1,bartlett(n+2),"g-*;bartlett;",triang(n),"r-+;triang;");
+%!
+%! subplot(111); title("");