fftshift

Purpose

Rearrange the outputs of fft and fft2.

Synopsis

Y = fftshift(X)

Description

Y = fftshift(X) rearranges the outputs of fft and fft2 by moving the zero frequency component to the center of the spectrum, which is sometimes a more convenient form.

If X is a vector, Y is a vector with the left and right halves swapped.

If X is a matrix, Y is a matrix with quadrants one and three swapped with quadrants two and four.

Examples

For any matrix X

Y = fft2(X)
has Y(1,1) = sum(sum(X)); the DC component of the signal is in the upper-left corner of the two-dimensional FFT. For

Z = fftshift(Y)
this DC component is near the center of the matrix.

See Also

fft, fft2

(c) Copyright 1994 by The MathWorks, Inc.