ifftshift

Inverse zero-frequency shift

Syntax

X = ifftshift(Y)

X = ifftshift(Y,dim)

Description

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.

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

Inverse Shift Vector Elements

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

Inverse Shift Matrix Rows

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

Y — Input array

vector | matrix | multidimensional array

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

dim — Dimension to operate along

positive integer scalar

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

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.

GPU Code Generation
Generate CUDA® code for NVIDIA® GPUs using GPU Coder™.

Thread-Based Environment

Run code in the background using MATLAB® backgroundPool or accelerate code with Parallel Computing Toolbox™ ThreadPool.

This function fully supports thread-based environments. For more information, see Run MATLAB Functions in Thread-Based Environment.

GPU Arrays

Accelerate code by running on a graphics processing unit (GPU) using Parallel Computing Toolbox™.

The ifftshift function fully supports GPU arrays. To run the function on a GPU, specify the input data as a gpuArray (Parallel Computing Toolbox). For more information, see Run MATLAB Functions on a GPU (Parallel Computing Toolbox).

Distributed Arrays

Partition large arrays across the combined memory of your cluster using Parallel Computing Toolbox™.

This function fully supports distributed arrays. For more information, see Run MATLAB Functions with Distributed Arrays (Parallel Computing Toolbox).

Version History

Introduced before R2006a