--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main/signal/tripuls.m	Wed Oct 10 19:54:49 2001 +0000
@@ -0,0 +1,70 @@
+## 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 2 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, write to the Free Software
+## Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+
+## 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, skew)
+
+  if nargin<1 || nargin>3,
+    usage("y = tripuls(t [, w [, skew]])");
+  endif
+
+  if nargin < 2, w = 1; endif
+  if nargin < 3, skew = 0; endif
+
+  y = zeros(size(t));
+  peak = skew*w/2;
+  dfi = do_fortran_indexing;
+  unwind_protect
+    do_fortran_indexing = 1;
+    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
+    do_fortran_indexing = dfi;
+  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); 
+%! oneplot(); title(""); xlabel(""); ylabel("");
+