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// Scilab ( http://www.scilab.org/ ) - This file is part of Scilab
// Copyright (C) 2012 - INRIA - Serge STEER
//
// This file must be used under the terms of the CeCILL.
// This source file is licensed as described in the file COPYING, which
// you should have received as part of this distribution. The terms
// are also available at
// http://www.cecill.info/licences/Licence_CeCILL_V2.1-en.txt
function demo_conv()
//create a signal
dt=0.02;
t=0:dt:1;
f=1;// frequency in Hertz
y=sin(2*%pi*f*t)+0.1*rand(t);
scf(1000);clf;
demo_viewCode("conv.dem.sce");
drawlater()
subplot(211)
plot(t,y) //given signal
//low pass 8 points wfir filter
Smooth=[0.1197912,0.1242239,0.1272323,0.1287527,0.1287527,0.1272323,0.1242239,0.1197912];
ys=conv(y,Smooth,"same");
plot(t,ys,"r")// filtered signal
legend([_("given noisy signal"),_("filtered signal")])
title(_("Signal"))
subplot(212)
//2 points derivative using convolution
plot(t(1:$-1),conv(ys,[1,-1],"valid")/dt,"r")
//3 points derivative using convolution
plot(t(1:$-2),conv(ys,[1, 0,-1]/2,"valid")/dt,"g")
legend([_("2 points convolution"),_("3 points convolution")])
title(_("Signal derivative estimate"))
drawnow()
endfunction
demo_conv()
clear demo_conv
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