# filters

DWT filter bank filters

## Syntax

``[Lo,Hi] = filters(fb)``

## Description

example

````[Lo,Hi] = filters(fb)` returns the lowpass (scaling) and highpass (wavelet) filters, `Lo` and `Hi`, respectively, for the discrete wavelet transform (DWT) filter bank `fb`.```

## Examples

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Obtain the lowpass and highpass filters for the order-4 symlet.

```fb = dwtfilterbank('Wavelet','sym4'); [Lo,Hi] = filters(fb)```
```Lo = 8×2 -0.0758 0.0322 -0.0296 -0.0126 0.4976 -0.0992 0.8037 0.2979 0.2979 0.8037 -0.0992 0.4976 -0.0126 -0.0296 0.0322 -0.0758 ```
```Hi = 8×2 -0.0322 -0.0758 -0.0126 0.0296 0.0992 0.4976 0.2979 -0.8037 -0.8037 0.2979 0.4976 0.0992 0.0296 -0.0126 -0.0758 -0.0322 ```

Confirm the filter bank is orthogonal.

`isOrthogonal(fb)`
```ans = logical 1 ```

## Input Arguments

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Discrete wavelet transform (DWT) filter bank, specified as a `dwtfilterbank` object.

## Output Arguments

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Lowpass (scaling) filters for the DWT filter bank, returned as an L-by-2 matrix. L is an even positive integer. The first column of `Lo` is the analysis filter, and the second column is the synthesis filter.

For orthogonal wavelets, the lowpass synthesis and lowpass analysis filters are time-reversed versions of each other.

Highpass (wavelet) filters for the DWT filter bank, returned as an L-by-2 matrix. L is an even positive integer. The first column of `Hi` is the analysis filter, and the second column is the synthesis filter.

For orthogonal wavelets, the highpass synthesis and highpass analysis filters are time-reversed versions of each other.

## Version History

Introduced in R2018a