# Convert Model Rate

Convert models between continuous time and discrete time and resample models in the Live Editor

## Open the Task

To add the **Convert Model Rate** task to a live script in
the MATLAB Editor:

On the

**Live Editor**tab, select**Task**>**Convert Model Rate**.In a code block in your script, type a relevant keyword, such as

`convert`

,`rate`

, or`c2d`

. Select`Convert Model Rate`

from the suggested command completions.

## Examples

## Parameters

`Model`

— Model to convert

LTI model

Select an LTI model. The list contains all suitable continuous-time or discrete-time dynamic system models in the MATLAB workspace, including:

Numeric LTI models such as

`tf`

,`ss`

, or`zpk`

models.Identified LTI models such as

`idss`

and`idtf`

. (Using identified models requires a System Identification Toolbox™ license.)

You can convert SISO models or MIMO models, with or without time delays, although
some conversion methods are only available for SISO models (see the
**Method** parameter description). You cannot use
**Convert Model Rate** to convert generalized LTI models
such as `genss`

or `uss`

, frequency-response data
models such as `frd`

, or process models
(`idproc`

).

`Sample Time`

— Target sample time

0.2 (default) | 0 | positive scalar

Specify the sample time of the converted model in units of
1/`TimeUnit`

, where `TimeUnit`

is the
`TimeUnit`

property of the input model.

To discretize a continuous-time model or resample a discrete-time model, enter the target sample time.

To convert a discrete-time model to continuous time, enter 0.

`Method`

— Rate conversion method

`Zero-order hold`

(default) | `First-order hold`

| `Bilinear (Tustin) approximation`

| ...

Choose a rate conversion method. Available methods are:

`Zero-order hold`

`First-order hold`

`Impulse-invariant discretization`

(continuous-to-discrete conversion of SISO models only)`Bilinear (Tustin) approximation`

`Zero-pole matching method`

`Least-squares method`

(continuous-to-discrete conversion of SISO models only)

For information about choosing a conversion method, see Continuous-Discrete Conversion Methods.

`Delay Order`

— Approximate order for estimating time delay

0 (default) | positive integer

When you convert the rate of a model that has a time delay, the
`Bilinear (Tustin) approximation`

or ```
Zero-pole
matching method
```

methods round the time delay to the nearest integer
multiple of the sample time. This rounding can degrade the accuracy of dynamics,
especially near the Nyquist frequency.

Set **Delay Order** to a nonzero integer to make
**Convert Model Rate** approximate the fractional portion
of the delay using a Thiran filter, instead of rounding. Use the smallest value that
yields sufficiently accurate rate-converted dynamics for your application. For more
information about Thiran filters, see `thiran`

.

`Prewarp Freq. (rad/s)`

— Prewarp frequency for bilinear (Tustin) method

0 (default) | positive scalar

When you discretize a continuous-time model, if your system has important dynamics
at a particular frequency that you want the rate conversion to preserve, you can use the
`Bilinear (Tustin) approximation`

method with frequency
prewarping. This method ensures a match between the original and converted responses at
the prewarp frequency you specify. See Continuous-Discrete Conversion Methods.

`Output Plot`

— Type of response plot

`Bode`

(default) | `Step`

| `Impulse`

| ...

**Convert Model Rate** automatically generates a
response plot to help you check that the dynamics important to your application are
preserved. Specify one of the following response plot types to compare the responses of
the original and converted models while you experiment with conversion
parameters.

`Bode`

`Step`

`Impulse`

`Pole-Zero`

The code generated by the task includes code to create the selected response plot.
To omit the response plot, select `None`

.

## Version History

**Introduced in R2019b**