# Documentation

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# sigmaplot

Plot singular values of frequency response and return plot handle

## Syntax

```h = sigmaplot(sys) sigmaplot(sys,{wmin,wmax}) sigmaplot(sys,w) sigmaplot(sys,w,TYPE) sigmaplot(AX,...) sigmaplot(..., plotoptions) ```

## Description

`h = sigmaplot(sys)` produces a singular value (SV) plot of the frequency response of the dynamic system `sys`. It also returns the plot handle `h`. You can use this handle to customize the plot with the `getoptions` and `setoptions` commands. Type

```help sigmaoptions ```

for a list of available plot options.

The frequency range and number of points are chosen automatically. See `bode` for details on the notion of frequency in discrete time.

`sigmaplot(sys,{wmin,wmax})` draws the SV plot for frequencies ranging between `wmin` and `wmax` (in `rad/TimeUnit`, where `TimeUnit` is the time units of the input dynamic system, specified in the `TimeUnit` property of `sys`).

`sigmaplot(sys,w)` uses the user-supplied vector `w` of frequencies, in `rad/TimeUnit`, at which the frequency response is to be evaluated. See `logspace` to generate logarithmically spaced frequency vectors.

`sigmaplot(sys,w,TYPE)` or `sigmaplot(sys,[],TYPE)` draws the following modified SV plots depending on the value of `TYPE`:

 TYPE = 1 --> SV of inv(SYS) TYPE = 2 --> SV of I + SYS TYPE = 3 --> SV of I + inv(SYS)

`sys` should be a square system when using this syntax.

`sigmaplot(AX,...)` plots into the axes with handle `AX`.

`sigmaplot(..., plotoptions)` plots the singular values with the options specified in `plotoptions`. Type

```help sigmaoptions ```

for more details.

## Examples

collapse all

Plot the singular value responses of a dynamic system.

```sys = rss(3,3,5); h = sigmaplot(sys);```

Set properties of the plot handle `h` to customize the plot. For example, change the plot units to Hz.

`setoptions(h,'FreqUnits','Hz');`

## Tips

You can change the properties of your plot, for example the units. For information on the ways to change properties of your plots, see Ways to Customize Plots.