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Nichols chart of frequency response

`nichols(`

creates a Nichols chart of the
frequency response of a dynamic system model
`sys`

)`sys`

. The plot displays the magnitude (in dB) and phase (in degrees)
of the system response as a function of frequency. `nichols`

automatically determines frequencies to plot based on system dynamics. Use `ngrid`

to superimpose Nichols chart grid lines on an existing SISO Nichols
chart.

If `sys`

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

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

If `sys`

is a model with complex coefficients, then
`nichols`

plot shows a contour comprised of both positive and
negative frequencies. For models with real coefficients, `nichols`

only
shows positive frequencies.

`nichols(___,`

plots the
response for frequencies specified by `w`

)`w`

.

If

`w`

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

, then`nichols`

plots the chart at frequencies ranging between`wmin`

and`wmax`

.If

`w`

is a vector of frequencies, then`nichols`

plots the chart 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

`nicholsplot`

instead.