# ifft2

## Purpose

Inverse 2-D fast Fourier transform.

## Synopsis

    Y = ifft2(X)
    Y = ifft2(X,m,n)

## Description

`ifft2(X)` returns the two-dimensional inverse fast Fourier transform of matrix `X`.

`ifft(X,m,n)` returns the `m-`by`-n` inverse transform.

## Examples

For any `X`, `ifft2(fft2(X))` equals `X` to within roundoff error. If `X` is real`,` `ifft2(fft2(X))` may have small imaginary parts.

## Algorithm

The algorithm for `ifft2(X)` is the same as the algorithm for `fft2(X)`, except for a sign change and scale factors of `[m,n] = size(X)`. The execution time is fastest when `m` and `n` are powers of 2 and slowest when they are large primes.

## See Also

    fft, fft2, fftshift,  filter, ifft
    dftmtx, freqz, specplot, and spectrum in the Signal Processing Toolbox

(c) Copyright 1994 by The MathWorks, Inc.