# FFTP

## Purpose:

Calculates the Fast Fourier transform
of a series in polar (Magnitude/Phase) form.

## Syntax:

FFTP(series, len)

series |
- |
Any series or multi-column table. |

len |
- |
Optional. An integer, the FFT length. Defaults
to the length of the input series. If len
> length(series), the series is padded with zeros. |

## Returns:

A complex series or table in Polar form.

## Example:

W1: gsin(1000, 0.001, 50)

W2: fft(w1, 1024)

W3: fftp(w1, 1024)

Although W2 and W3 are identical in terms
of the complex result, W2 contains the FFT result in Cartesian form, a + bi, while
W3 represents the result in polar form *Me*^{iθ}.
For plotting purposes, W2 displays the real part of the FFT and W3 displays
the magnitude part.

## Remarks:

The FFTP result is complex polar and the
magnitude of the resultant series is plotted. A *mixed
radix* algorithm is employed to compute the FFT.

FFTP uses the same algorithm as the FFT but is slightly slower because it calculates magnitude/phase.

Use SPECTRUM
to produce a normalized magnitude plot.

## See Also:

DFT

FFT2

FFT

IFFTP

PSD

SPECTRUM

## References:

Oppenheim and Schafer.

Digital Signal Processing

Prentice Hall, 1975

Digital Signal Processing Committee

Programs for Digital
Signal Processing

I.E.E.E. Press, 1979