/**
* Computes the correlation of fdata with gdata. The value of the output at index i is the sum
* over j of fdata[i+j]*gdata[j], although using the FFT is much faster than direct sum.
*
* @see http://www.ulib.org/webRoot/Books/Numerical_Recipes/bookcpdf.html section 13-2
*/
public static final float[] correlate(float[] fdata, float[] gdata) {
if (fdata.length != gdata.length) {
throw new IllegalArgumentException(
"fdata and gdata must have same length. " + fdata.length + " " + gdata.length);
}
Cmplx[] fTrans = fft(fdata);
Cmplx[] gTrans = fft(gdata);
for (int i = 0; i < fTrans.length; i++) {
fTrans[i] = Cmplx.mul(fTrans[i], gTrans[i].conjg());
} // end of for (int i=0; i<gdata.length; i++)
return fftInverse(fTrans, fdata.length);
}
public static final Cmplx mul(Cmplx a, double b) {
return Cmplx.mul(a, new Cmplx(b, 0));
}
public static final Cmplx mul(double a, Cmplx b) {
return Cmplx.mul(new Cmplx(a, 0), b);
}
