Forums

cross correlation implemenation

Started by Unknown May 5, 2006
For starters, I hope I'm not off topic.

I'm looking for a C/C++ cross correlation implemention.   Something
akin to matlab xcorr.  I'm perusing the matlab source for xcorr and -
it's so say the least - intimidating.  Trying to convert my matlab
source to C++ but would hate to re-invent the wheel if a sound
implementation of these exists someplace.

Thanks in advance

<forums_mp@hotmail.com> wrote in message 
news:1146877765.787911.67510@u72g2000cwu.googlegroups.com...
> > For starters, I hope I'm not off topic. > > I'm looking for a C/C++ cross correlation implemention. Something > akin to matlab xcorr. I'm perusing the matlab source for xcorr and - > it's so say the least - intimidating. Trying to convert my matlab > source to C++ but would hate to re-invent the wheel if a sound > implementation of these exists someplace. > > Thanks in advance >
Enjoy: Call with two vectors of data in x and y. Let z point to memory for result. Allocate length_x + length_y-1 locations. lenx and leny are the respective lengths of data. // performs straight convolution by Clay S. Turner // for correlattion just reverse the order of sequence y; ConvolveFunction(double *z, double *x, double *y, int lenx, int leny) { double *zptr,s,*xp,*yp; int lenz; int i,n,n_lo,n_hi; lenz=lenx+leny-1; zptr=z; for (i=0;i<lenz;i++) { s=0.0; n_lo=0>(i-leny+1)?0:i-leny+1; n_hi=lenx-1<i?lenx-1:i; xp=x+n_lo; yp=y+i-n_lo; for (n=n_lo;n<=n_hi;n++) { s+=*xp * *yp; xp++; yp--; } *zptr=s; zptr++; } }