# Documentation

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# step

Package: dsp

Decompose input with dyadic filter bank

## Syntax

```Y = step(dydan,X) ```

## Description

### Note

Starting in R2016b, instead of using the `step` method to perform the operation defined by the System object™, you can call the object with arguments, as if it were a function. For example, ```y = step(obj,x)``` and `y = obj(x)` perform equivalent operations.

`Y = step(dydan,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

expand all

Note: This example runs only in R2016b or later. If you are using an earlier release, replace each call to the function with the equivalent `step` syntax. For example, myObject(x) becomes step(myObject,x).

Sampling frequency 1 kHz input length 1024

```t = 0:.001:1.023; x = square(2*pi*30*t); xn = x' + 0.08*randn(length(x),1);```

Default asymmetric structure with Daubechies order 3 extremal phase wavelet

```dydan = dsp.DyadicAnalysisFilterBank; Y = dydan(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```

Note: This example runs only in R2016b or later. If you are using an earlier release, replace each call to the function with the equivalent `step` syntax. For example, myObject(x) becomes step(myObject,x).

Sampling frequency 1 kHz input length 1024.

```t = 0:.001:1.023; x = square(2*pi*30*t); xn = x' + 0.08*randn(length(x),1);```

symmetric structure with Daubechies order 3 extremal phase wavelets.

```dydan = dsp.DyadicAnalysisFilterBank('TreeStructure',... 'Symmetric'); Y = dydan(xn); D1 = Y(1:256); % subband approx. [375,500] Hz D2 = Y(257:512); % subband approx. [250,375] Hz D3 = Y(513:768); % subband approx. [125,250] Hz Approx = Y(769:1024); % subband approx. [0, 125] Hz```