net.sf.dsp4j.octave.packages.signal_1_0

Introduction

Here is the source code for net.sf.dsp4j.octave.packages.signal_1_0_11.Cheb.java
Source

package net.sf.dsp4j.octave.packages.signal_1_0_11;

import java.util.Arrays;
import net.sf.dsp4j.octave_3_2_4.OctaveBuildIn;
import org.apache.commons.math3.complex.Complex;
import org.apache.commons.math3.util.FastMath;

/*
## Copyright (C) 2002 Andr Carezia
##
## 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, see <http://www.gnu.org/licenses/>.
    
## Usage:  cheb (n, x)
##
## Returns the value of the nth-order Chebyshev polynomial calculated at
## the point x. The Chebyshev polynomials are defined by the equations:
##
##           / cos(n acos(x),    |x| <= 1
##   Tn(x) = |
##           \ cosh(n acosh(x),  |x| > 1
##
## If x is a vector, the output is a vector of the same size, where each
## element is calculated as y(i) = Tn(x(i)).
    
## Author:  Andr Carezia <acarezia@uol.com.br>
## Description:  Value of the Chebyshev polynomials
 */
public class Cheb {

    public static double[] cheb(int n, double[] x) {

        if (n <= 0) {
            throw new IllegalArgumentException("cheb: n has to be a positive integer");
        }

        if (x.length == 0) {
            return new double[0];
        }
        //# avoid resizing latencies
        double[] T = new double[x.length];
        for (int i = 0; i < x.length; i++) {
            if (Math.abs(x[i]) > 1) {
                T[i] = FastMath.cos(n * FastMath.acos(x[i]));
            } else {
                T[i] = FastMath.cosh(n * FastMath.acosh(x[i]));
            }
        }
        return T;
    }
}
net.sf.dsp4j.octave.packages.signal_1_0_11.Cheb.java Source code

Introduction

Source
