The applet below shows how the butterfly diagram is used to calculate the FFT. The first row of scrollbars change the real parts of the samples, the second row changes the imaginary part.

If the input is real, then the real parts of the output are symmetric and the imaginary parts are antisymmetric.

If the input is imaginary, then the real parts of the output are antisymmetric and the imaginary parts are symmetric.

COPYRIGHT © 2007 Cuthbert Nyack.