The following list of commands can be very useful for future reference.
Use "help

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.

Non-standard Matlab commands are highlighted in green.

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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 |

c2dm | Continuous system to discrete system |

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 |

dimpulse | Impulse response of discrete-time linear systems, see also dstep |

dlqr | Linear-quadratic requlator design for discrete-time systems, see also lqr |

dlsim | Simulation of discrete-time linear systems, see also lsim |

dstep | Step response of discrete-time linear systems, see also stairs |

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, dlsim |

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, sigrid, zgrid |

legend | Graph legend |

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, see also dlqr |

lsim | Simulate a linear system, see also step, impulse, dlsim. |

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 the current plot (to a printer or postscript file) | |

pzmap | Pole-zero map of linear systems |

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 |

series | Series interconnection of Linear time-independent systems |

sgrid | Generate grid lines of constant damping ratio (zeta) and natural frequency (Wn), see also jgrid, sigrid, zgrid |

sigrid | Generate grid lines of constant settling time (sigma), see also jgrid, sgrid, zgrid |

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 |

stairs | Stairstep plot for discreste response, see also dstep |

step | Plot the step response, see also impulse, lsim, dlsim. |

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 |

zgrid | Generates grid lines of constant damping ratio (zeta) and natural frequency (Wn), see also sgrid, jgrid, sigrid |

zp2ss | Pole-zero to state-space representation, see also ss2zp |

zp2tf | Pole-zero to transfer function representation, see also tf2zp |

*10/22/96 YS, 8/18/97 DK*