variance.c

语音CELP压缩解压源代码（C语音)

/**************************************************************************
*
* ROUTINE
*               variance
*
* FUNCTION
*
*               calculates variance of the input array
*
* SYNOPSIS
*               subroutine variance(arr, no, var, avg)
*
*   formal
*
*                       data    I/O
*       name            type    type    function
*       -------------------------------------------------------------------
*       arr		float	i	input data array
*	no		int	i	number of elements in array
*	var		float	o	variance
*	avg		real	i/o	average
*
***************************************************************************
*
* DESCRIPTION
*
*
***************************************************************************
*
* CALLED BY
*
*       smoothcbgain   smoothtau
*
* CALLS
*
*
*
**************************************************************************/
variance(arr, no, var, avg)
int no;
float arr[], *var, *avg;
{
  int i;
  float sum, sum2;

  for (sum = 0.0, i = 0; i < no; i++)
    sum += arr[i];
  *avg = sum / no;
  for (sum2 = 0.0, i = 0; i < no; i++)
    sum2 += (*avg - arr[i]) * (*avg - arr[i]);
  *var = sum2 / (no - 1);
}