Where to start the conjugation as input to IFFT?

Hello guys,

I want to give a conjugate symmetric input to the ifft function, but I am confused where to grab the first point to conjugate since my data X can either have even or odd number of points.

X is a complex frequency domain data and has a size of N-by-1.

If N is even or odd, do we append the conjugation as follows?

if ~mod(N, 2)
% for even N
    X = [X; conj( X(end-1:-1:2) )];
else
% for odd N
    X = [X; conj( X(end:-1:2) )];
end
x = ifft(X);

I am thinking that

X = [X; conj( X(end-1:-1:2) )];

might be the right one either if N is even or odd, but I am not sure.

Answer 1

[Joh Yhan]

If you are expecting a real number output from ifft, then your code is correct.