I have a periodic series of 360 values. How can I use the fftw c libraries to get the amplitude and phase of the first, second, third and fourth harmonic?
If I do this for N=360
I can get the 360-point Discrete Fourier Transform (DFT) where output_array[k] is the real portion of the kth element of a halfcomplex array while output_array[N-k] is the imaginary portion of the kth value.
So if I want the amplitude or magnitude(??) of the first harmonic should I do this?
Is that correct? then the amplitude of the second harmonic will be the same but with output_array and output_array[N-2] and so on right?
And then how can I get the phase of the first, second, third and fourth harmonic with the infor from the DFT?
For a reference to fftw see here www.fftw.org/fftw3.pdf