Nyquist plot with additional plot customization options

`h = nyquistplot(sys)`

nyquistplot(sys,{wmin,wmax})

nyquistplot(sys,w)

nyquistplot(sys1,sys2,...,w)

nyquistplot(AX,...)

nyquistplot(..., plotoptions)

`h = nyquistplot(sys)`

draws the Nyquist
plot of the dynamic
system model `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 nyquistoptions

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.

`nyquistplot(sys,{wmin,wmax})`

draws the
Nyquist plot for frequencies 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`

).

`nyquistplot(sys,w)`

uses the user-supplied
vector `w`

of frequencies (in `rad/TimeUnit`

,
where `TimeUnit`

is the time units of the input dynamic
system, specified in the `TimeUnit`

property
of `sys`

) at which the Nyquist response is to be
evaluated. See `logspace`

to
generate logarithmically spaced frequency vectors.

`nyquistplot(sys1,sys2,...,w)`

draws the
Nyquist plots of multiple models `sys1`

,`sys2`

,...
on a single plot. The frequency vector `w`

is optional.
You can also specify a color, line style, and marker for each system,
as in

nyquistplot(sys1,'r',sys2,'y--',sys3,'gx')

`nyquistplot(AX,...)`

plots into the axes
with handle `AX`

.

`nyquistplot(..., plotoptions)`

plots the
Nyquist response with the options specified in `plotoptions`

.
Type

help nyquistoptions

for more details.

**Customize Nyquist Plot Frequency Units**

Plot the Nyquist frequency response and change the units to rad/s.

sys = rss(5); h = nyquistplot(sys); % Change units to radians per second. setoptions(h,'FreqUnits','rad/s');

Compare the frequency responses of identified state-space models
of order 2 and 6 along with their `1-std`

confidence
regions rendered at every 50th frequency sample.

load iddata1 sys1 = n4sid(z1, 2) % discrete-time IDSS model of order 2 sys2 = n4sid(z1, 6) % discrete-time IDSS model of order 6

Both models produce about 76% fit to data. However, `sys2`

shows
higher uncertainty in its frequency response, especially close to `Nyquist`

frequency
as shown by the plot:

w = linspace(10,10*pi,256); h = nyquistplot(sys1,sys2,w); setoptions(h,'ConfidenceRegionDisplaySpacing',50,'ShowFullContour','off');

Right-click to turn on the confidence region characteristic
by using the **Characteristics-> Confidence Region**.

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