DFT / FFT Software for the MacintoshWritten by Paul Bourke
First version 1991, updated 1996
DFT_FFT is a Macintosh utility that reads either real or complex series and computes either the DFT or FFT. It is designed as a data exploratory/investigation tool rather than a total analysis package.
The time series is displayed as follows, note that in this example the file contained two columns and was opened as real/imaginary even though the imaginary term is 0. Note also that no assumptions are made as to the meaning of the index, it could be a time series, frequency, spatial, etc.
For example the magnitude/phase graph is shown below. The form of this shouldn't be a surprise since the input series above looks like a sinusoid plus noise, there aren't an integer number of cycles in the series so there is spectral leakage. The first N/2 samples are the positive frequencies from DC to Nyquist, the second N/2-1 samples are the negative frequencies.
Or the power/phase
Or the polar plot