MATLAB Function Reference
ifft2

Two-dimensional inverse discrete Fourier transform

Syntax

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

Description

```Y = ifft2(X) ``` returns the two-dimensional inverse discrete Fourier transform (DFT) of `X`, computed with a fast Fourier transform (FFT) algorithm. The result `Y` is the same size as `X.`

```Y = ifft2(X,m,n) ``` returns the `m-`by`-n` inverse fast Fourier transform of matrix `X`.

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 for i`fft2` depends on the length of the transform. It is fastest for powers of two. It is almost as fast for lengths that have only small prime factors. It is typically several times slower for lengths that are prime or which have large prime factors.

`dftmtx` and `freqz` in the Signal Processing Toolbox, and:
`fft2`, `fftshift`, `ifft`, `ifftn`, `ifftshift`