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Matlab Commands List

The following list of commands can be very useful for future reference. Use "help" in Matlab for more information on how to use the commands.

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

Command
Description
abs Absolute value
acker Compute the K matrix to place the poles of A-BK, see also place
axis Set the scale of the current plot, see also plot, figure
bode Draw the Bode plot, see also logspace, margin, nyquist1
clf Clear figure (use clg in Matlab 3.5)
cloop Closed-loop transfer function
conv Convolution (useful for multiplying polynomials), see also deconv
ctrb The controllability matrix, see also obsv
deconv Deconvolution and polynomial division, see also conv
det Find the determinant of a matrix
eig Compute the eigenvalues of a matrix
eps Matlab's numerical tolerance
figure Create a new figure or redefine the current figure, see also subplot, axis
for For, next loop
format Number format (significant digits, exponents)
function Creates function m-files
grid Draw the grid lines on the current plot
gtext Add a piece of text to the current plot, see also text
help HELP!
hold Hold the current graph, see also figure
if Conditionally execute statements
imag Returns the imaginary part of a complex number, see also real
impulse Impulse response of continuous-time linear systems, see also step, lsim
input Prompt for user input
inv Find the inverse of a matrix
jgrid Generate grid lines of constant damping ratio (zeta) and settling time (sigma), see also sgrid, sigma
length Length of a vector, see also size
linspace Returns a linearly spaced vector
lnyquist1 Produce a Nyquist plot on a logarithmic scale, see also nyquist1
log natural logarithm, also log10: common logarithm
loglog Plot using log-log scale, also semilogx/semilogy
logspace Returns a logarithmically spaced vector
lqr Linear quadratic regulator design for continuous systems
lsim Simulate a linear system, see also step, impulse.
margin Returns the gain margin, phase margin, and crossover frequencies, see also bode
norm Norm of a vector
nyquist1 Draw the Nyquist plot, see also lnyquist1. Note this command was written to replace the Matlab standard command nyquist to get more accurate Nyquist plots.
obsv The observability matrix, see also ctrb
ones Returns a vector or matrix of ones, see also zeros
place Compute the K matrix to place the poles of A-BK, see also acker
plot Draw a plot, see also figure, axis, subplot.
poly Returns the characteristic polynomial
polyadd Add two different polynomials
polyval Polynomial evaluation
print Print the current plot (to a printer or postscript file)
rank Find the number of linearly independent rows or columns of a matrix
real Returns the real part of a complex number, see also imag
rlocfind Find the value of k and the poles at the selected point
rlocus Draw the root locus
roots Find the roots of a polynomial
rscale Find the scale factor for a full-state feedback system
set Set(gca,'Xtick',xticks,'Ytick',yticks) to control the number and spacing of tick marks on the axes
sgrid Generate grid lines of constant damping ratio (zeta) and natural frequency (Wn), see also jgrid, sigma
sigma Generate grid lines of constant settling time (sigma), see also jgrid, sgrid
size Gives the dimension of a vector or matrix, see also length
sqrt Square root
ss2tf State-space to transfer function representation, see also tf2ss
ss2zp State-space to pole-zero representation, see also zp2ss
step Plot the step response, see also impulse, lsim.
subplot Divide the plot window up into pieces, see also plot, figure
text Add a piece of text to the current plot, see also title, xlabel, ylabel, gtext
tf2ss Transfer function to state-space representation, see also ss2tf
tf2zp Transfer function to Pole-zero representation, see also zp2tf
title Add a title to the current plot
wbw Returns the bandwidth frequency given the damping ratio and the rise or settling time.
xlabel/ylabel Add a label to the horizontal/vertical axis of the current plot, see also title, text, gtext
zeros Returns a vector or matrix of zeros
zp2ss Pole-zero to state-space representation, see also ss2zp
zp2tf Pole-zero to transfer function representation, see also tf2zp

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10/22 1996 YS