FFT2

2-D fast Fourier transform

Syntax

y = fft2（X)

y = fft2（X,m,n)

Description

y = fft2（X)returns thetwo-dimensional Fourier transformof a matrix using a fast Fourier transform algorithm, which is equivalent to computingFFT(fft(X).').'. IfX是一个多维数组，然后FFT2takes the 2-D transform of each dimension higher than 2. The outputYis the same size asX.

example

y = fft2（X,m,n)truncatesXor padsXwith trailing zeros to form anm-by-nmatrix before computing the transform.Yism-by-n. IfX是一个多维数组，然后FFT2shapes the first two dimensions ofXaccording tom和n.

Examples

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2-D Transform

打开实时脚本

The 2-D Fourier transform is useful for processing 2-D signals and other 2-D data such as images.

使用重复块创建和绘制2-D数据。

P = peaks(20); X = repmat(P,[5 10]); imagesc(X)

Compute the 2-D Fourier transform of the data. Shift the zero-frequency component to the center of the output, and plot the resulting 100-by-200 matrix, which is the same size asX.

y = fft2（X); imagesc(abs(fftshift(Y)))

PadXwith zeros to compute a 128-by-256 transform.

y = fft2（x，2^nextPow2（100），2^nextPow2（200））;imagesc（abs（fftshift（y）））;

Input Arguments

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`X`—Input array
matrix|multidimensional array

Input array, specified as a matrix or a multidimensional array. IfXis of typesingle, thenFFT2natively computes in single precision, andYis also of typesingle. Otherwise,Yis returned as typedouble.

`m`—变换行的数量
positive integer scalar

变换行的数量, specified as a positive integer scalar.

`n`—Number of transform columns
positive integer scalar

Number of transform columns, specified as a positive integer scalar.

More About

collapse all

2-D Fourier Transform

This formula defines the discrete Fourier transformYof anm-by-nmatrixX:

ω_m和ω_nare complex roots of unity:

iis the imaginary unit.p和jare indices that run from 0 tom–1, andq和kare indices that run from 0 ton–1. This formula shifts the indices forX和Yby 1 to reflect matrix indices in MATLAB^®.

Extended Capabilities

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

Usage notes and limitations:

对于MEX输出，MATLAB Coder™使用MATLAB用于FFT算法的库。对于独立的C/C ++代码，默认情况下，代码生成器生成用于FFT算法的代码，而不是生成FFT库调用。要生成针对特定安装的FFTW库的呼叫，请提供FFT库回调类。有关FFT库回调类的更多信息，请参阅coder.fftw.StandaloneFFTW3Interface.
For simulation of aMATLAB Functionblock, the simulation software uses the library that MATLAB uses for FFT algorithms. For C/C++ code generation, by default, the code generator produces code for FFT algorithms instead of producing FFT library calls. To generate calls to a specific installed FFTW library, provide an FFT library callback class. For more information about an FFT library callback class, seecoder.fftw.StandaloneFFTW3Interface.

GPU Code Generation
使用GPU CODER™为NVIDIA®GPU生成CUDA®代码。

GPU Arrays
使用并行计算工具箱™在图形处理单元（GPU）上运行加速代码。

Usage notes and limitations:

The outputYis always complex even if all the imaginary parts are zero.

For more information, seeRun 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运行具有分布式数组的MATLAB功能(Parallel Computing Toolbox).

FFT2

Syntax

Description

Examples

2-D Transform

Input Arguments

`X`—Input array
matrix|multidimensional array

`m`—变换行的数量
positive integer scalar

`n`—Number of transform columns
positive integer scalar

More About

2-D Fourier Transform

Extended Capabilities

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

GPU Code Generation
使用GPU CODER™为NVIDIA®GPU生成CUDA®代码。

GPU Arrays
使用并行计算工具箱™在图形处理单元（GPU）上运行加速代码。

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

See Also

Introduced before R2006a

MATLAB Documentation

金宝app

Try MATLAB, Simulink, and Other Products

FFT2

Syntax

Description

Examples

2-D Transform

Input Arguments

X—Input arraymatrix|multidimensional array

m—变换行的数量positive integer scalar

n—Number of transform columnspositive integer scalar

More About

2-D Fourier Transform

Extended Capabilities

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

GPU Code Generation使用GPU CODER™为NVIDIA®GPU生成CUDA®代码。

GPU Arrays使用并行计算工具箱™在图形处理单元（GPU）上运行加速代码。

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

See Also

Introduced before R2006a

MATLAB Documentation

金宝app

Try MATLAB, Simulink, and Other Products

`X`—Input array
matrix|multidimensional array

`m`—变换行的数量
positive integer scalar

`n`—Number of transform columns
positive integer scalar

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

GPU Code Generation
使用GPU CODER™为NVIDIA®GPU生成CUDA®代码。

GPU Arrays
使用并行计算工具箱™在图形处理单元（GPU）上运行加速代码。

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