## Correlation on DSP KIT TMS320C6713 Simulator

December 15, 2010 Coded in C++ for the TI C67x
``````#include <stdio.h>
#include <math.h>

double pi=3.14159;

float x[50],y[50];
float r[100];

void correlation(float *x,float *y, int nx, int ny);

int main()
{

int ii;
for(ii=0;ii<50  ;ii++)
{
x[ii]=sin(2.0*pi*ii*3/50);
y[ii]=sin(2.0*pi*ii*3/50);

}

correlation(x,y,50,50);

printf("Complete.\n");

return 0;
}

void correlation(float *x,float *y, int nx, int ny)
{
int n=50,delay=0,maxdelay=50;
int i,j;
double mx,my,sx,sy,sxy,denom;

/* Calculate the mean of the two series x[], y[] */
mx = 0;
my = 0;
for (i=0;i<n;i++)
{
mx += x[i];
my += y[i];
}
mx /= n;
my /= n;

/* Calculate the denominator */
sx = 0;
sy = 0;
for (i=0;i<n;i++)
{
sx += (x[i] - mx) * (x[i] - mx);
sy += (y[i] - my) * (y[i] - my);
}
denom = sqrt(sx*sy);

/* Calculate the correlation series */
for (delay=-maxdelay;delay<maxdelay;delay++)
{
sxy = 0;
for (i=0;i<n;i++)
{
j = i + delay;
if (j < 0 || j >= n)
continue;
else
sxy += (x[i] - mx) * (y[j] - my);
// Or should it be (?)
/* if (j < 0 || j >= n)
sxy += (x[i] - mx) * (-my);
else
sxy += (x[i] - mx) * (y[j] - my);*/

}
r[delay+maxdelay]= ( sxy / denom);``````