Listing 2 Code for a Simple Filter

 void simple_filter(double *x, double *y, int N,
double a, double b)
 {
    double y0 = 0, y1 = 0;
    int i = 0;
    
    for(; i < N; i++)
    {
      
      y[i] = a*y0 + b*y1 + x[i];
      y1 = y0;
      y0 = y[i];
    }
 }