Index: MATLAB Commands List

Following is a list of commands used in the Control Tutorials for MATLAB and Simulink. Use help in MATLAB for more information on how to use any of these commands.

In these tutorials, we use commands/functions from MATLAB, from the Control Systems Toolbox, as well as some functions which we wrote ourselves. For those functions which are not standard in MATLAB, we give links to their descriptions. For more information on writing MATLAB functions, see the function page.

absAbsolute value
ackerCompute the K matrix to place the poles of A-BK, see also place
axisSet the scale of the current plot, see also plot, figure
bodeDraw the Bode plot, see also logspace, margin, nyquist1
c2dContinuous system to discrete system
clfClear figure
convConvolution (useful for multiplying polynomials), see also deconv
ctrbThe controllability matrix, see also obsv
deconvDeconvolution and polynomial division, see also conv
detFind the determinant of a matrix
dlqrLinear-quadratic regulator design for discrete-time systems, see also lqr
eigCompute the eigenvalues of a matrix
epsMATLAB's numerical tolerance
feedbackConnect linear systems in a feedback loop
figureCreate a new figure or redefine the current figure, see also subplot, axis
forFor loop
formatNumber format (significant digits, exponents)
functionCreates function m-files
gridDraw the grid lines on the current plot
gtextAdd a piece of text to the current plot, see also text
helpMatlab help documentation
holdHold the current graph, see also figure
ifConditionally execute statements
imagReturns the imaginary part of a complex number, see also real
impulseImpulse response of linear systems, see also step, lsim
inputPrompt for user input
invFind the inverse of a matrix
legendGraph legend
lengthLength of a vector, see also size
linspaceReturns a linearly spaced vector
lnyquistProduce a Nyquist plot on a logarithmic scale, see also nyquist1
logNatural logarithm, also log10: common logarithm
loglogPlot using log-log scale, also semilogx/semilogy
logspaceReturns a logarithmically spaced vector
lqrLinear quadratic regulator design for continuous systems, see also dlqr
lsimSimulate a linear system, see also step, impulse
marginReturns the gain margin, phase margin, and crossover frequencies, see also bode
minrealProduces a minimal realization of a system (forces pole/zero cancellations)
normNorm of a vector
nyquist1Draw the Nyquist plot, see also lnyquist. Note this command was written to replace the MATLAB standard command nyquist to get more accurate Nyquist plots.
obsvThe observability matrix, see also ctrb
onesReturns a vector or matrix of ones, see also zeros
placeCompute the K matrix to place the poles of A-BK, see also acker
plotDraw a plot, see also figure, axis, subplot.
polyReturns the characteristic polynomial
polyvalPolynomial evaluation
printPrint the current plot (to a printer or postscript file)
pzmapPole-zero map of linear systems
rankFind the number of linearly independent rows or columns of a matrix
realReturns the real part of a complex number, see also imag
rlocfindFind the value of k and the poles at the selected point
rlocusDraw the root locus
rootsFind the roots of a polynomial
rscaleFind the scale factor for a full-state feedback system
setSet(gca,'Xtick',xticks,'Ytick',yticks) to control the number and spacing of tick marks on the axes
sgridGenerate grid lines of constant damping ratio (zeta) and natural frequency (Wn), see also sigrid, zgrid
sizeGives the dimension of a vector or matrix, see also length
sqrtSquare root
ssCreate state-space models or convert LTI model to state space, see also tf
ssdataAccess to state-space data. See also tfdata
stairsStairstep plot for discrete response
stepPlot the step response, see also impulse, lsim
subplotDivide the plot window up into pieces, see also plot, figure
textAdd a piece of text to the current plot, see also title, xlabel, ylabel, gtext
tfCreation of transfer functions or conversion to transfer function, see also ss
tfdataAccess to transfer function data, see also ssdata
titleAdd a title to the current plot
wbwReturns the bandwidth frequency given the damping ratio and the rise or settling time.
xlabel/ylabelAdd a label to the horizontal/vertical axis of the current plot, see also title, text, gtext
zerosReturns a vector or matrix of zeros
zgridGenerates grid lines of constant damping ratio (zeta) and natural frequency (Wn), see also sgrid, sigrid