Nyquist plot with additional plot customization options (2025)

Open Live Script

rng("default")sys = rss(5);h = nyquistplot(sys);

setoptions(h,'PhaseUnits','rad','Grid','on');

plotoptions = nyquistoptions('cstprefs');

plotoptions.PhaseUnits = 'rad';plotoptions.Grid = 'on';nyquistplot(sys,plotoptions);

Open Live Script

sys = tf(100,[1,2,1]);h = nyquistplot(sys);

opt = getoptions(h)

opt = FreqUnits: 'rad/s' MagUnits: 'dB' PhaseUnits: 'deg' ShowFullContour: 'on' ConfidenceRegionNumberSD: 1 ConfidenceRegionDisplaySpacing: 5 IOGrouping: 'none' InputLabels: [1x1 struct] OutputLabels: [1x1 struct] InputVisible: {'on'} OutputVisible: {'on'} Title: [1x1 struct] XLabel: [1x1 struct] YLabel: [1x1 struct] TickLabel: [1x1 struct] Grid: 'off' GridColor: [0.1500 0.1500 0.1500] XLim: {[-20 100]} YLim: {[-80 80]} XLimMode: {'auto'} YLimMode: {'auto'}

opt.Title

ans = struct with fields: String: 'Nyquist Diagram' FontSize: 11 FontWeight: 'bold' FontAngle: 'normal' Color: [0 0 0] Interpreter: 'tex'

opt.Title.String = 'Nyquist Plot of sys';setoptions(h,opt)

Open Live Script

sys = tf(100,[1,2,1]);h = nyquistplot(sys);

zoomcp(h)

Open Live Script

load iddata1sys1 = n4sid(z1,2); sys2 = n4sid(z1,6);w = linspace(10,10*pi,256);h = nyquistplot(sys1,sys2,w);

setoptions(h,'ConfidenceRegionDisplaySpacing',50,... 'ShowFullContour','off');

Open Live Script

J = [8 -3 -3; -3 8 -3; -3 -3 8];F = 0.2*eye(3);A = -J\F;B = inv(J);C = eye(3);D = 0;sys_mimo = ss(A,B,C,D);size(sys_mimo)

State-space model with 3 outputs, 3 inputs, and 3 states.

h = nyquistplot(sys_mimo);

p = getoptions(h)

p = FreqUnits: 'rad/s' MagUnits: 'dB' PhaseUnits: 'deg' ShowFullContour: 'on' ConfidenceRegionNumberSD: 1 ConfidenceRegionDisplaySpacing: 5 IOGrouping: 'none' InputLabels: [1x1 struct] OutputLabels: [1x1 struct] InputVisible: {3x1 cell} OutputVisible: {3x1 cell} Title: [1x1 struct] XLabel: [1x1 struct] YLabel: [1x1 struct] TickLabel: [1x1 struct] Grid: 'off' GridColor: [0.1500 0.1500 0.1500] XLim: {3x1 cell} YLim: {3x1 cell} XLimMode: {3x1 cell} YLimMode: {3x1 cell}

setoptions(h,'ShowFullContour','off','Grid','on');

• Continuous-time or discrete-time numeric LTI models, such as tf, zpk, or ss models.

• Sparse state-space models, such as sparss or mechss models. Frequency grid w must be specified for sparse models.

• Generalized or uncertain LTI models such as genss or uss (Robust Control Toolbox) models. (Using uncertain models requires Robust Control Toolbox™ software.)

  • For tunable control design blocks, the function evaluates the model at its current value to plot the frequency response data.

  • For uncertain control design blocks, the function plots the nominal value and random samples of the model.

• Frequency-response data models such as frd models. For such models, the function plots the Nyquist plot at frequencies defined in the model.

• Identified LTI models, such as idtf (System Identification Toolbox), idss (System Identification Toolbox), or idproc (System Identification Toolbox) models. (Using identified models requires System Identification Toolbox™ software.)

• If w is a cell array of the form {wmin,wmax}, then the function computes the response at frequencies ranging between wmin and wmax.

• If w is a vector of frequencies, then the function computes the response at each specified frequency. For example, use logspace to generate a row vector with logarithmically spaced frequency values.