Documentation

filter2

2-D digital filter

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Syntax

Y = filter2(H,X)
Y = filter2(H,X,shape)

Description

example

Y = filter2(H,X)applies a finite impulse response filter to a matrix of dataXaccording to coefficients in a matrixH.

example

Y = filter2(H,X,shape)returns a subsection of the filtered data according toshape. For example,Y = filter2(H,X,'valid')returns only filtered data computed without zero-padded edges.

Examples

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Open Live Script

You can digitally filter images and other 2-D data using thefilter2function, which is closely related to theconv2function.

Create and plot a 2-D pedestal with interior height equal to one.

A = zeros(10); A(3:7,3:7) = ones(5); mesh(A)

Filter the data inAaccording to a filter coefficient matrixH, and return the full matrix of filtered data.

H = [1 2 1; 0 0 0; -1 -2 -1]; Y = filter2(H,A,'full'); mesh(Y)

RotateH180 degrees and convolve the result withA. The output is equivalent to filtering the data inAwith the coefficients inH.

C = conv2(A,rot90(H,2)); mesh(C)

Input Arguments

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Coefficients of the rational transfer function, specified as a matrix.

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

Input data, specified as a matrix. If one or both ofXandHare of typesingle, then the output is also of typesingle. Otherwise,filter2returns typedouble.

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

Subsection of the filtered data, specified as one of these values:

  • 'same'— Return the central part of the filtered data, which is the same size asX.

  • 'full'— Return the full 2-D filtered data.

  • 'valid'— Return only parts of the filtered data that are computed without zero-padded edges.

Algorithms

Thefilter2function filters data by taking the 2-D convolution of the inputXand the coefficient matrixHrotated 180 degrees. Specifically,filter2(H,X,shape)相当于conv2(X,rot90(H,2),shape).

Extended Capabilities

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

See Also

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Introduced before R2006a

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