# 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.

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 |

c2d | Continuous system to discrete system |

clf | Clear figure |

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 |

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

eig | Compute the eigenvalues of a matrix |

eps | MATLAB's numerical tolerance |

feedback | Connect linear systems in a feedback loop |

figure | Create a new figure or redefine the current figure, see also subplot, axis |

for | For 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 | Matlab help documentation |

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 linear systems, see also step, lsim |

input | Prompt for user input |

inv | Find the inverse of a matrix |

legend | Graph legend |

length | Length of a vector, see also size |

linspace | Returns a linearly spaced vector |

lnyquist | 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 |

margin | Returns the gain margin, phase margin, and crossover frequencies, see also bode |

minreal | Produces a minimal realization of a system (forces pole/zero cancellations) |

norm | Norm of a vector |

nyquist1 | Draw the Nyquist plot, see also lnyquist. 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 |

polyval | Polynomial evaluation |

print | 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 |

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

size | Gives the dimension of a vector or matrix, see also length |

sqrt | Square root |

ss | Create state-space models or convert LTI model to state space, see also tf |

ssdata | Access to state-space data. See also tfdata |

stairs | Stairstep plot for discrete response |

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 |

tf | Creation of transfer functions or conversion to transfer function, see also ss |

tfdata | Access to transfer function data, see also ssdata |

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, sigrid |