# The Large Time-Frequency Analysis Toolbox

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# FFRACFT - Approximate fast fractional Fourier transform

## Usage

frf=ffracft(f,a)
frf=ffracft(f,a,dim)


## Description

ffracft(f,a) computes an approximation of the fractional Fourier transform of the signal f to the power a. If f is multi-dimensional, the transformation is applied along the first non-singleton dimension.

ffracft(f,a,dim) does the same along dimension dim.

ffracft takes the following flags at the end of the line of input arguments:

 'origin' Rotate around the origin of the signal. This is the same action as the dft, but the signal will split in the middle, which may not be the correct action for data signals. This is the default. 'middle' Rotate around the middle of the signal. This will not break the signal in the middle, but the dft cannot be obtained in this way.

## Examples:

The following example shows a rotation of the ltfatlogo test signal:

sgram(ffracft(ltfatlogo,.3,'middle'),'lin','nf');


## References:

A. Bultheel and S. Martínez. Computation of the Fractional Fourier Transform. Appl. Comput. Harmon. Anal., 16(3):182-202, 2004.