nicholsoptions
Plot options for nicholsplot
Description
Use the nicholsoptions function to create a
NicholsOptions object. Use this object to customize the appearance of a
Nichols plot created using nicholsplot and override the plot preferences
for the MATLAB® session in which you create the Nichols plot.
The options you specify for a NicholsOptions object correspond to
properties of a NicholsPlot chart
object.
Creation
Description
plotoptions = nicholsoptionsnicholsplot. You can use these options to customize the Nichols plot
appearance using the command line. This syntax is useful when you want to write a script
to generate plots that look the same regardless of the preference settings of the
MATLAB session in which you run the script.
plotoptions = nicholsoptions("cstprefs")
Properties
Object Functions
nicholsplot | Plot Nichols frequency response of dynamic system |
Examples
For this example, use the plot handle to change the title, turn on the grid, and set axis limits.
Generate a random state-space model with 5 states and create the Nichols plot with chart object np.
rng("default")
sys = rss(5);
np = nicholsplot(sys);
Change the title, enable the grid, and set axis limits.
np.Title.String = "Nichols Frequency Response"; xlim([-2 4]) ylim([3.3 4.3]) grid on
Alternatively, you can also use the nicholsoptions command to specify the required plot options. First, create an options set based on the toolbox preferences.
plotoptions = nicholsoptions('cstprefs');Change the desired properties of the options set.
plotoptions.Title.String = 'Nichols Frequency Response'; plotoptions.Grid = 'on'; plotoptions.XLim = {[-2,4]}; plotoptions.YLim = {[3.3,4.3]}; nicholsplot(sys,plotoptions);
Depending on your own toolbox preferences, the plot you obtain might look different from this plot. Only the properties that you set explicitly, in this example Title, Grid, XLim and YLim, override the toolbox preferences.
For this example, create a Nichols plot that uses 15-point red text for the title. This plot should look the same, regardless of the preferences of the MATLAB session in which it is generated.
First, create a default options set using nicholsoptions.
plotoptions = nicholsoptions;
Next, change the required properties of the options set plotoptions.
plotoptions.Title.FontSize = 15; plotoptions.Title.Color = [1 0 0]; plotoptions.FreqUnits = 'Hz'; plotoptions.Grid = 'on';
Now, create a Nichols plot using the options set plotoptions.
nicholsplot(tf(1,[1,1]),{0,15},plotoptions);
Because plotoptions begins with a fixed set of options, the plot result is independent of the toolbox preferences of the MATLAB session.
For this example, create a Nichols plot of the following continuous-time SISO dynamic system. Then, turn the grid on and rename the plot.
Create the transfer function sys.
sys = tf([1 0.1 7.5],[1 0.12 9 0 0]);
Next, create the options set using nicholsoptions and change the required plot properties.
plotoptions = nicholsoptions; plotoptions.Grid = 'on'; plotoptions.Title.String = 'Nichols Plot of Transfer Function';
Now, create the Nichols plot with the custom option set plotoptions.
nicholsplot(sys,plotoptions)
nicholsplot automatically selects the plot range based on the system dynamics.
For this example, compare the Nichols response of a parametric model, identified from input/output data, to a non-parametric model identified using the same data. Identify parametric and non-parametric models based on the data.
Load the data and create the parametric and non-parametric models using tfest and spa, respectively.
load iddata2 z2; w = linspace(0,10*pi,128); sys_np = spa(z2,[],w); sys_p = tfest(z2,2);
spa and tfest require System Identification Toolbox™ software. The model sys_np is a non-parametric identified model while, sys_p is a parametric identified model.
Create an options set to turn phase matching and the grid on. Then, create a Nichols plot that includes both systems using this options set.
plotoptions = nicholsoptions; plotoptions.PhaseMatching = 'on'; plotoptions.Grid = 'on'; plotoptions.XLim = {[-240,0]}; h = nicholsplot(sys_p,'r.-.',sys_np,'b.-.',w,plotoptions); legend('Parametric Model','Non-Parametric model');
Create an options set, and set the phase units and grid option.
P = nicholsoptions; P.PhaseUnits = 'rad'; P.Grid = 'on';
Use the options set to generate a Nichols plot. Note the phase units and grid in the plot.
h = nicholsplot(tf(1,[1,.2,1,0]),P);
Version History
Introduced in R2008a
