File content as of revision 0:da10b9c9db7a:

/**
 *****************************************************************************
 * File Name    : util.c
 *
 * Title        : Utility functions Source File
 * Revision     : 0.1
 * Notes        :
 * Target Board : mbed NXP LPC1768
 * Tool Chain   : ????
 *
 * Revision History:
 * When         Who         Description of change
 * -----------  ----------- -----------------------
 * 2012/07/10   Hiroshi M   init
 *****************************************************************************
 *
 * Copyright (C) 2012 Hiroshi M, MIT License
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
 * and associated documentation files (the "Software"), to deal in the Software without restriction,
 * including without limitation the rights to use, copy, modify, merge, publish, distribute,
 * sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all copies or
 * substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING
 * BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 *
 **/

/* Includes ----------------------------------------------------------------- */
#include "util.h"

/* Private typedef ---------------------------------------------------------- */
/* Private define ----------------------------------------------------------- */
/* Private macro ------------------------------------------------------------ */
/* Private variables -------------------------------------------------------- */
/* Private function prototypes -----------------------------------------------*/

/**
 * least squares method
 *
 */
int lsm(int *y, int x)
{
    int n;
    static long a0, a1, a2;
    long s01 = 0, s02 = 0, s11 = 0, s12 = 0;

    if (x == 0) {
        for (n = 0; n < N; n++) {
            s01 += n;
            s02 += (long)y[n];
            s11 += n * n;
            s12 += n * (long)y[n];
        }

        a0 = (s02 * s11 - s01 * s12) / (N * s11 - s01 * s01);
        a1 = (N * s12 - s01 * s02);
        a2 = (N * s11 - s01 * s01 * 2);
    }
    return (int)(a0 + a1 * (N + x) / a2);
}


int xabs(int x,int y)
{
    if(x >= y) {
        return (x - y);
    } else {
        return (y - x);
    }
}