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/*!
* \file
* \brief Implementation of window functions
* \author Tony Ottosson, Tobias Ringstrom, Pal Frenger and Adam Piatyszek
*
* -------------------------------------------------------------------------
*
* IT++ - C++ library of mathematical, signal processing, speech processing,
* and communications classes and functions
*
* Copyright (C) 1995-2008 (see AUTHORS file for a list of contributors)
*
* 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., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*
* -------------------------------------------------------------------------
*/
#include <itpp/signal/window.h>
namespace itpp {
vec hamming(int n)
{
vec t(n);
if (n == 1)
t(0) = 0.08;
else
for (int i=0;i<n;i++)
t[i]=(0.54-0.46*std::cos(2.0*pi*i/(n-1)));
return t;
}
vec hanning(int n)
{
vec t(n);
for (int i=0;i<n;i++)
t(i) = 0.5 * (1.0 - std::cos(2.0*pi*(i+1)/(n+1)));
return t;
}
// matlab version
vec hann(int n)
{
vec t(n);
for (int i=0;i<n;i++)
t(i) = 0.5 * (1.0 - std::cos(2.0*pi*i/(n-1)));
return t;
}
vec blackman(int n)
{
vec t(n);
for (int i=0;i<n;i++)
t(i) = 0.42 - 0.5 * std::cos(2.0*pi*i/(n-1)) + 0.08 * std::cos(4.0*pi*i/(n-1));
return t;
}
vec triang(int n)
{
vec t(n);
if (n % 2) { // Odd
for (int i=0; i<n/2; i++)
t(i) = t(n-i-1) = 2.0*(i+1)/(n+1);
t(n/2) = 1.0;
} else
for (int i=0; i<n/2; i++)
t(i) = t(n-i-1) = (2.0*i+1)/n;
return t;
}
vec sqrt_win(int n)
{
vec t(n);
if (n % 2) { // Odd
for (int i=0; i<n/2; i++)
t(i) = t(n-i-1) = std::sqrt(2.0*(i+1)/(n+1));
t(n/2) = 1.0;
} else
for (int i=0; i<n/2; i++)
t(i) = t(n-i-1) = std::sqrt((2.0*i+1)/n);
return t;
}
} // namespace itpp
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