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Hello,

I'm trying to implement a cascading iir and here's my code for the first
second order z transform.  I'm I going about this correctly? My output is
good till a particular value and then it starts having problems.  Any help
or links to a good example would be great!

Thanks,
Grant

float b[3] = {1,2,1};
float a[3] = {1,-1.9985996261556458,0.99952100328066507};
float y[151]={0};
int i=0;
char wait;

while(i<151)
{
       x[i] *= 7.0818881108085789e-7;
if(i==0)
       y[i] = x[i];
if(i==1)
       y[i] = x[i] + b[1]*x[i-1] - a[1]*y[i-1];
if (i>1)
       y[i] = x[i] + b[1]*x[i-1] + b[2]*x[i-2] - a[1]*y[i-1] -
a[2]*y[i-2];
cout<<y[i]<<" "<<i<<"\n";

i++;
}

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x = x * 7.0818881108085789e-7;

y = b[0]*x + d[0];
d[0] = b[1]*x - a[1]*y + d[1];
d[1] = b[2]*x - a[2]*y + d[2];

cout<<y<<" "<<x<<" "<<x1<<"
"<<x2<<"\n";
i+=.001;
same results

--- In c...@yahoogroups.com, "Grant Jennings" <gtjennings@...> wrote:
>
> Hello,
> 
> I'm trying to implement a cascading iir and here's my code for the first
> second order z transform.  I'm I going about this correctly? My
output is
> good till a particular value and then it starts having problems. 
Any help
> or links to a good example would be great!
> 
> Thanks,
> Grant
> 
> float b[3] = {1,2,1};
> float a[3] = {1,-1.9985996261556458,0.99952100328066507};
> float y[151]={0};
> int i=0;
> char wait;
> 
> while(i<151)
> {
>        x[i] *= 7.0818881108085789e-7;
> if(i==0)
>        y[i] = x[i];
> if(i==1)
>        y[i] = x[i] + b[1]*x[i-1] - a[1]*y[i-1];
> if (i>1)
>        y[i] = x[i] + b[1]*x[i-1] + b[2]*x[i-2] - a[1]*y[i-1] -
> a[2]*y[i-2];
> cout<<y[i]<<" "<<i<<"\n";
> 
> i++;
> }
>

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