# filt

Specify discrete transfer functions in DSP format

## Syntax

## Description

Use `filt`

to create discrete-time transfer function models in
digital signal processing (DSP) form for use with Control System Toolbox™ linear analysis and control design tools. To apply a filter to vector data, see
`filter`

.

In DSP, it is conventional to use transfer functions as rational expressions in
*z*^{−1} and to order the numerator and denominator
terms in *ascending* powers of
*z*^{−1}. For example:

$$H\left({z}^{-1}\right)=\frac{2+{z}^{-1}}{1+0.4{z}^{-1}+2{z}^{-2}}$$

`filt`

creates a `tf`

object with the
`Variable`

property set to `'z^-1'`

. For more information,
see `tf`

.

creates a discrete-time transfer function model in DSP form using the coefficients specified
in the `sys`

= filt(`numerator`

,`denominator`

)`numerator`

and `denominator`

arguments. The
sample time is left unspecified. For more information, see the `tf`

reference page.

sets the sample time of the discrete-time transfer function.`sys`

= filt(`numerator`

,`denominator`

,`ts`

)

## Examples

## Input Arguments

## Output Arguments

## Version History

**Introduced before R2006a**