Add a useful package (from Source forge) for octave

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

diff --git a/octave_packages/signal-1.1.3/tripuls.m b/octave_packages/signal-1.1.3/tripuls.m
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+## Copyright (C) 2001 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: y = tripuls(t, w, skew)
+##
+## Generate a triangular pulse over the interval [-w/2,w/2), sampled at
+## times t.  This is useful with the function pulstran for generating a
+## series pulses.
+##
+## skew is a value between -1 and 1, indicating the relative placement
+## of the peak within the width.  -1 indicates that the peak should be
+## at -w/2, and 1 indicates that the peak should be at w/2.
+##
+## Example
+##   fs = 11025;  # arbitrary sample rate
+##   f0 = 100;    # pulse train sample rate
+##   w = 0.3/f0;  # pulse width 3/10th the distance between pulses
+##   auplot(pulstran(0:1/fs:4/f0, 0:1/f0:4/f0, 'tripuls', w), fs);
+##
+## See also: pulstran
+
+function y = tripuls (t, w = 1, skew = 0)
+
+  if nargin<1 || nargin>3,
+    print_usage;
+  endif
+
+  y = zeros(size(t));
+  peak = skew*w/2;
+  try wfi = warning("off", "Octave:fortran-indexing");
+  catch wfi = 0;
+  end
+  unwind_protect
+    idx = find(t>=-w/2 & t <= peak);
+    if (idx) y(idx) = ( t(idx) + w/2 ) / ( peak + w/2 ); endif
+    idx = find(t>peak & t < w/2);
+    if (idx) y(idx) = ( t(idx) - w/2 ) / ( peak - w/2 ); endif
+  unwind_protect_cleanup
+    warning(wfi);
+  end_unwind_protect
+endfunction
+
+%!assert(tripuls(0:1/100:0.3,.1), tripuls([0:1/100:0.3]',.1)');
+%!assert(isempty(tripuls([],.1)));
+%!demo
+%! fs = 11025;  # arbitrary sample rate
+%! f0 = 100;    # pulse train sample rate
+%! w = 0.5/f0;  # pulse width 1/10th the distance between pulses
+%! subplot(211); ylabel("amplitude"); xlabel("time (ms)");
+%! title("graph shows 5 ms pulses at 0,10,20,30 and 40 ms");
+%! auplot(pulstran(0:1/fs:4/f0, 0:1/f0:4/f0, 'tripuls', w), fs);
+%! subplot(212);
+%! title("graph shows 5 ms pulses at 0,10,20,30 and 40 ms, skew -0.5");
+%! auplot(pulstran(0:1/fs:4/f0, 0:1/f0:4/f0, 'tripuls', w, -0.5), fs);
+%! title(""); xlabel(""); ylabel("");