Hi
My question is more about Maths than D lang,
I am hoping, maybe somebody worked with AutoCorrelation function
before.
auto autoCorrelation(R)(R range)
if (isRandomAccessRange!R)
{
auto residual = residualPowerOf2(range.length); // Find how
many zeros to add
auto fftResult = range.chain(repeat(0, residual)).fft(); //
Takes FFT
//First zip each element of fft with conjagute of fft
auto autoCorrResult = fftResult.zip(fftResult.map!(a => a *
a.conj())).
map!( a=> a[0] * a[1] ). // Than multiple them
inverseFft(). // Than take inverse
dropBack(residual);//Drop the additional zeros
auto finalResult = autoCorrResult.take(1). // Take DC element
chain(autoCorrResult[$/2..$]).//Take last half to
beginning
chain(autoCorrResult[1..$/2]). // First(negative lags)
to end
map!(a => a.re); // I just need real part
return finalResult ;
}
My autocorrelation method return some crazy values(finalResult[0]
= -101652). I am mostly suspicious about calculations to set
"finalResult" variable.
Also is there any performance issues? can I make this faster?
