The **FFT...** dialog box can be used either on a table or on a plot. It is used to compute a direct or inverse FFT. See the FFT section in the Analysis chapter for an example.

SciDAVis will create a new plot window with the FFT amplitude curve, and a new table which contains the real part, the imaginary part, the amplitude, and the angle of the FFT.

If the *Normalize Amplitude* check box is on, the amplitude curve is normalized to 1. If the *Shift Results* check box is on, the frequencies are shifted in order to obtain a centered x-scale.

In the case of a table, you must select the sampling column (X-values) and two columns for Y-values. If they are complex numbers, the first column is the real part of Y-values and the second is the imaginary part. If Y-values are simple reals, you must select the same column for real and imaginary part.

By default, the *Sampling Interval* corresponds to the interval between X-values. Giving a smaller value makes no sense, but you can increase this value in order to sample less values