Control System Toolbox™

nicholsplot - Plot Nichols frequency responses and return plot handle

Syntax

h = nicholsplot(sys)
nicholsplot(sys,{wmin,wmax})
nicholsplot(sys,w)
nicholsplot(sys1,sys2,...,w)
nicholsplot(AX,...)
nicholsplot(..., plotoptions)

Description

h = nicholsplot(sys) draws the nichols plot of the LTI model sys (created with tf, zpk, ss, or frd). It also returns the plot handle h. You can use this handle to customize the plot with the getoptions and setoptions commands. Type

help nicholsoptions 

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.

nicholsplot(sys,{wmin,wmax}) draws the Nichols plot for frequencies between wmin and wmax (in rad/s).

nicholsplot(sys,w) uses the user-supplied vector w of frequencies, in radians/second, at which the Nichols response is to be evaluated. See logspace to generate logarithmically spaced frequency vectors.

nicholsplot(sys1,sys2,...,w) draws the Nichols plots of multiple LTI 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

nicholsplot(sys1,'r',sys2,'y--',sys3,'gx').

nicholsplot(AX,...) plots into the axes with handle AX.

nicholsplot(..., plotoptions) plots the Nichols plot with the options specified in plotoptions. Type

help nicholsoptions 

for more details.

Remarks

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.

Example

Generate Nichols plot and use plot handle to change frequency units to Hz

sys = rss(5);
h = nicholsplot(sys);
% Change units to Hz 
setoptions(h,'FreqUnits','Hz');

See Also

getoptions, nichols, nicholsoptions, setoptions

nicholsoptions

norm