## 2D FFT Test Page

FFT2D evaluates the Fast Fourier Transform, fft, of an
analytic function of two spatial variables. The function string is parsed and evaluated
on an x-y grid before the fft is performed. The transformed data can then be passed to other
Physlets, such as SPlotter, using a data connection. The FFT data source is identified using
the getID() method. It provides a data set containing "surfacedata".

### Gutter

The gutter can be used to drop high frequencies. For example, a gutter of 16
will drop 32 data points since both positive and negative frequencies will be excluded from the
output. The number of fft points should be larger then the gutter.

*Limitation: Array must be square.*