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Nyquist plot of frequency response

`nyquist(`

creates a Nyquist plot of the
frequency response of a dynamic system
model
`sys`

)`sys`

. The plot displays real and imaginary parts of the system
response as a function of frequency.

`nyquist`

plots a contour comprised of both positive and negative
frequencies. The plot also shows arrows to indicate the direction of increasing frequency
for each branch. `nyquist`

automatically determines frequencies to plot
based on system dynamics.

If `sys`

is a multi-input, multi-output (MIMO) model, then
`nyquist`

produces an array of Nyquist plots, each plot showing the
frequency response of one I/O pair.

If `sys`

is a model with complex coefficients, then the positive
and negative branches are not symmetric.

`nyquist(___,`

plots system
responses for frequencies specified by `w`

)`w`

.

If

`w`

is a cell array of the form`{wmin,wmax}`

, then`nyquist`

plots the response at frequencies ranging between`wmin`

and`wmax`

.If

`w`

is a vector of frequencies, then`nyquist`

plots the response at each specified frequency. The vector`w`

can contain both negative and positive frequencies.

You can use `w`

with any of the input-argument combinations in
previous syntaxes.

When you need additional plot customization options, use

`nyquistplot`

instead.Two zoom options that apply specifically to Nyquist plots are available from the right-click menu :

**Full View**— Clips unbounded branches of the Nyquist plot, but still includes the critical point (–1, 0).**Zoom on (-1,0)**— Zooms around the critical point (–1, 0). To access critical-point zoom programmatically, use the`zoomcp`

command. For more information, see`nyquistplot`

.

To activate data markers that display the real and imaginary values at a given frequency, click anywhere on the curve. The following figure shows a

`nyquist`

plot with a data marker.

`sigma`

(Control System Toolbox) | `bode`

| `nyquistplot`