dspl/cheby__poly1_8c_source.html

/*

* Copyright (c) 2015-2024 Sergey Bakhurin

* Digital Signal Processing Library [http://dsplib.org]

*

* This file is part of libdspl-2.0.

*

* is free software: you can redistribute it and/or modify

* it under the terms of the GNU Lesser    General Public License as published by

* the Free Software Foundation, either version 3 of the License, or

* (at your option) any later version.

*

* DSPL 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 Lesser General Public License

* along with Foobar.    If not, see <http://www.gnu.org/licenses/>.

*/


#include <stdlib.h>

#include <string.h>

#include <math.h>

#include "dspl.h"


#ifdef DOXYGEN_ENGLISH


#endif

#ifdef DOXYGEN_RUSSIAN


#endif

int DSPL_API cheby_poly1(double* x, int n, int ord, double* y)

{

    int k, m;

    double t[2];


    if(!x || !y)

        return ERROR_PTR;

    if(n < 1)

        return ERROR_SIZE;

    if(ord<0)

        return ERROR_POLY_ORD;

    if(ord==0)

    {

        for(k = 0; k < n; k++)

        {

            y[k] = 1.0;

        }

        return RES_OK;

    }


    if(ord==1)

    {

        memcpy(y, x, n*sizeof(double));

        return RES_OK;

    }


    for(k = 0; k < n; k++)

    {

        m = 2;

        t[1] = x[k];

        t[0] = 1.0;

        while(m <= ord)

        {

            y[k] = 2.0 * x[k] *t[1] - t[0];

            t[0] = t[1];

            t[1] = y[k];

            m++;

        }

    }

    return RES_OK;

}