This repository was archived by the owner on Nov 19, 2020. It is now read-only.
This repository was archived by the owner on Nov 19, 2020. It is now read-only.
DFT functions in AForge.Math.FourierTransform and Accord.Math.Transforms #257
Description
for simple complex array [ 3+1i 9+14i 11+7i 40+31i]..
Accord.Math.Transforms.FourierTransform2.DFT(Forward) changes the array to
[ 63+53i -25+25i -35-37i 9-37i ]
AForge.Math.FourierTransform.DFT(Forward) changes the array to
[ 0.75+0.25i 2.25+3.5i 2.75+1.75i 10+7.75i ]
In Matlab answers same value with Accord.Math.Transforms.FourierTransform2.DFT.
Their function bodies(Accord and AForge) are almost same but direction is reversed.
And backward return operation of AForge may be incorrect.
In Accord..
for (int i = 0; i < c.Length; i++)
{
...
c[i] = new Complex(sumRe, sumIm);
}
if (direction == FourierTransform.Direction.Backward)
{
for (int i = 0; i < c.Length; i++)
data[i] = c[i] / n;
}
else
{
...
}
but AForge..
for (int i = 0; i < dst.Length; i++)
{
for (int j = 0; j < data.Length; j++)
{
...
dst[i] += new Complex(re, im);
}
}
// copy elements
if (direction == Direction.Forward) //<< reversed direction
{
// devide also for forward transform
for (int i = 0; i < data.Length; i++)
data[i] /= n; //<< not using "dst" array
}
else
{
...
}
I think it needs to be validate.
(why same functions are exist?)