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# step

Package: dsp

Decompose input with dyadic filter bank

Y = step(H,X)

## Description

Y = step(H,X) computes the subband decomposition of the input X and outputs the dyadic subband decomposition in Y as a single concatenated column vector or matrix of coefficients. Each column of X is treated as an independent input, and the number of rows of X must be a multiple of ${2}^{N},$ where N is the value of the NumLevels property. The elements of Y are ordered with the highest frequency subband first followed by subbands in decreasing frequency

## Examples

Subband ordering for level-two asymmetric tree structure:

```t = 0:.001:1.023;
% Sampling frequency 1 kHz input length 1024
x= square(2*pi*30*t);
xn = x' + 0.08*randn(length(x),1);
% Default asymmetric structure with
% Daubechies order 3 extremal phase wavelet
Y = step(H,xn);
% Level 2 yields 3 subbands (two detail-one approximation)
% Nyquist frequency is 500 Hz
D1 =Y(1:512); % subband approx. [250, 500] Hz
D2 = Y(513:768); % subband approx. [125, 250] Hz
Approx = Y(769:1024); % subband approx. [0,125] Hz```

Subband ordering for symmetric tree structure:

```t = 0:.001:1.023;
% Sampling frequency 1 kHz input length 1024
x= square(2*pi*30*t);
xn = x' + 0.08*randn(length(x),1); % symmetric structure with
% Daubechies order 3 extremal phase wavelet