Documentation

ifftshift

Inverse zero-frequency shift

Description

example

X = ifftshift(Y) rearranges a zero-frequency-shifted Fourier transform Y back to the original transform output. In other words, ifftshift undoes the result of fftshift.

• If Y is a vector, then ifftshift swaps the left and right halves of Y.

• If Y is a matrix, then ifftshift swaps the first quadrant of Y with the third, and the second quadrant with the fourth.

• If Y is a multidimensional array, then ifftshift swaps half-spaces of Y along each dimension.

example

X = ifftshift(Y,dim) operates along the dimension dim of Y. For example, if Y is a matrix whose rows represent multiple 1-D transforms, then ifftshift(Y,2) swaps the halves of each row of Y.

Examples

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You can use the fftshift and ifftshift functions to swap left and right halves of a vector.

Create a vector containing an odd number of elements, and swap the left and right sides of the vector using the fftshift function.

V = [1 2 3 4 5 6 7];
X = fftshift(V)
X = 1×7

5     6     7     1     2     3     4

Use the ifftshift function to swap the left and right sides of X. The result is the same as the original vector V.

Y = ifftshift(X)
Y = 1×7

1     2     3     4     5     6     7

Calling the fftshift function twice does not necessarily reconstruct the original input.

fftshift(fftshift(V))
ans = 1×7

2     3     4     5     6     7     1

Rearrange the rows of a matrix to shift the nonnegative elements to the left.

Y = [-2 -1 0 1 2;
-10 -5 0 5 10];
X = ifftshift(Y,2)
X = 2×5

0     1     2    -2    -1
0     5    10   -10    -5

Input Arguments

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Input array, specified as a vector, a matrix, or a multidimensional array.

Data Types: double | single | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | logical
Complex Number Support: Yes

Dimension to operate along, specified as a positive integer scalar. If no value is specified, then ifftshift swaps along all dimensions.

• Consider an input matrix Yc. The operation ifftshift(Yc,1) swaps halves of each column of Yc. • Consider an input matrix Yr. The operation ifftshift(Yr,2) swaps halves of each row of Yr. Data Types: double | single | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | logical