wthresh

Soft or hard thresholding

Syntax

Y = wthresh(X,sorh,T)

Description

example

Y = wthresh(X,sorh,T) returns the soft or hard thresholding, indicated by sorh, of the vector or matrix X. T is the threshold value.

Examples

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Generate a signal and set a threshold.

y = linspace(-1,1,100);
thr = 0.4;

Perform hard and soft thresholding.

ythard = wthresh(y,'h',thr);
ytsoft = wthresh(y,'s',thr);

Plot the results and compare with the original signal.

subplot(1,3,1)
plot(y,y)
ylim([-1 1])
title('Original Signal')
subplot(1,3,2)
plot(y,ythard)
ylim([-1 1])
title('Hard Threshold')
subplot(1,3,3)
plot(y,ytsoft)
ylim([-1 1])
title('Soft Threshold')

Input Arguments

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Input data to threshold, specified as a real-valued vector or matrix.

Data Types: double

Type of thresholding to perform:

  • 's' — Soft thresholding

  • 'h' — Hard thresholding

Threshold value, specified as a positive real number.

Output Arguments

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Thresholded data, returned as a real-valued vector or matrix. Y has the same dimensions as X.

Algorithms

If sorh is 's', Y is the soft thresholding of X: Y=sign(X)·(|X|T)+ where

(x)+={xifx00otherwise

Soft thresholding is wavelet shrinkage.

If sorh is 'h', Y is the hard thresholding of X: Y=X·1(|X|>T) where

1(|X|>T)={1if|X|>T0otherwise

Hard thresholding is cruder than soft thresholding.

Extended Capabilities

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

Introduced before R2006a