Suppose I have a list a=[1,2,3,4] and have already calculated its DFT: fft(a)=[10.+0.j, -2.+2.j, -2.+0.j, -2.-2.j].
Now I'd like to pad a with different amount of zeros to b (pad with two zeros): b=[1,2,3,4,0,0] and want to find fft(b). Is there an efficient way to reuse the result of fft(a) to get fft(b)? by efficient I mean it's faster than directly calculate fft(b)
Thanks for any help!!