fft(z, inverse=F) mvfft(z, inverse=F)
z
| a real or complex value array containing the values to be transformed. |
inverse
|
if TRUE, the inverse transform is computed
(the inverse has a + in the exponent of e and
divides the values by 1/length(x) before transforming).
|
z is a vector, the value computed and returned by fft is
the univariate Fourier transform of the sequence of values in z.
When z contains an array, fft computes and returns
the multivariate (spatial) transform.
By contrast, mvfft takes a real or complex matrix as argument,
and returns a similar shaped matrix, but with each column
replaced by its discrete Fourier transform.
This is useful for analysing vector-valued series.
The FFT is fastest when the length of of the series being transformed is highly composite (i.e. has many factors). If this is not the case, the transform may take a long time to compute and will use a large amount of memory.
convolve, nextn.