[Octave-cvsupdate] SF.net SVN: octave:[8613] trunk/octave-forge/main/signal/inst/sigmoid_train .m

[<car...@us...>]

Revision: 8613
          http://octave.svn.sourceforge.net/octave/?rev=8613&view=rev
Author:   carandraug
Date:     2011-09-27 13:18:11 +0000 (Tue, 27 Sep 2011)
Log Message:
-----------
sigmoid_train: new function to signal package

Added Paths:
-----------
    trunk/octave-forge/main/signal/inst/sigmoid_train.m

Added: trunk/octave-forge/main/signal/inst/sigmoid_train.m
===================================================================
--- trunk/octave-forge/main/signal/inst/sigmoid_train.m	                        (rev 0)
+++ trunk/octave-forge/main/signal/inst/sigmoid_train.m	2011-09-27 13:18:11 UTC (rev 8613)
@@ -0,0 +1,113 @@
+%% Copyright (c) 2011 Juan Pablo Carbajal <car...@if...>
+%% 
+%%    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
+%%    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{y} = sigmoid_train(@var{t}, @var{ranges}, @var{rc})
+%%
+%% Evaluates a train of sigmoid functions at @var{t}.
+%%
+%% The number and duration of each sigmoid is determined from @var{ranges}. Each
+%% row of @var{ranges} represents a real interval, e.g. if sigmod @code{i} starts
+%% at @code{t=0.1} and ends at @code{t=0.5}, then @code{@var{ranges}(i,:) = [0.1
+%% 0.5]}.
+%% The input @var{rc} is a array that defines the rising and falling time 
+%% constants of each sigmoids. Its size must equal the size of @var{ranges}.
+%%
+%% Run @code{demo sigmoid_train} to some examples of the use of this function.
+%%
+%% @seealso{}
+%% @end deftypefn
+
+function envelope = sigmoid_train (t, range, timeconstant)
+
+  % number of sigmoids
+  nRanges = size (range, 1);
+
+  %% Parse time constants
+  if isscalar (timeconstant)
+    %% All bumps have the same time constant and are symmetric
+    timeconstant = timeconstant * ones (nRanges,2);
+  end
+
+  if isvector (timeconstant)
+    %% All bumps have different time constant but are symmetric
+    if length(timeconstant) ~= nRanges
+      error('signalError','Length of time constant must equal number of ranges.')
+    end
+    if isrow (timeconstant)
+      timeconstant = timeconstant';
+    end
+    timeconstant = repmat (timeconstant,1,2);
+  end
+
+  %% Make sure t is horizontal
+  flag_transposed = false;
+  if iscolumn (t)
+   t               = t';
+   [ncol nrow]     = size (t);
+   flag_transposed = true;
+  end
+
+  % Compute arguments of each sigmoid
+  T    = repmat (t, nRanges, 1);
+  RC1  = repmat (timeconstant(:,1), 1, nrow);
+  RC2  = repmat (timeconstant(:,2), 1, nrow);
+  a_up = (repmat (range(:,1), 1 ,nrow) - T)./RC1;
+  a_dw = (repmat (range(:,2), 1 ,nrow) - T)./RC2;
+
+  % Evaluate the sigmoids and mix them
+  Y        = 1 ./ ( 1 + exp (a_up) ) .* (1 - 1 ./ ( 1 + exp (a_dw) ) );
+  envelope = max(Y,[],1);
+
+  if flag_transposed
+    envelope = envelope';
+  end
+
+end
+
+%!demo
+%! % Vectorized 
+%! t = linspace (0, 2, 500);
+%! range = [0.1 0.4; 0.6 0.8; 1 2];
+%! rc = [1e-2 1e-2; 1e-3 1e-3; 2e-2 2e-2];
+%! y = sigmoid_train (t, range, rc);
+%!
+%! close all
+%! for i=1:3 
+%!     patch ([range(i,[2 2]) range(i,[1 1])], [0 1 1 0],...
+%!               'facecolor', [1 0.8 0.8],'edgecolor','none');
+%! end
+%! hold on; plot (t, y, 'b;Sigmoid train;','linewidth',2); hold off
+%! xlabel('time'); ylabel('S(t)')
+%! title ('Vectorized use of sigmoid_train')
+%! axis tight
+
+%!demo
+%! % On demand 
+%! tspan = [0 2];
+%! ran = [0.5 1; 1.5 1.7];
+%! rc = 3e-2;
+%! dxdt = @(t_,x_) [ x_(2); sigmoid_train(t_, ran, rc) ];
+%! [t y] = ode45(dxdt,tspan,[0 0]);
+%!
+%! close all
+%! for i=1:2 
+%!     patch ([ran(i,[2 2]) ran(i,[1 1])], [0 1 1 0],...
+%!               'facecolor', [1 0.8 0.8],'edgecolor','none');
+%! end
+%! hold on; plot (t, y(:,2), 'b;Speed;','linewidth',2); hold off
+%! xlabel('time'); ylabel('V(t)')
+%! title ('On demand use of sigmoid_train')
+%! axis tight

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