Advanced MATLAB Commands and Functions

Other Useful Functions and Commands

Listed below are a few of the many MATLAB commands/functions. Use the help command for more detailed information on the commands and functions.

help	Prints list of all the topics for help
demo	Runs demonstrations: list the topics for which demos are available
whos	Lists variables in memory
what	Lists the M-files, MAT-files and MEX-files in the current working directory
size	Provides row and column dimensions: returns the size of the predefined matrix if it is given a proper argument
length	Shows vector length
clear	Clears workspace, all variables get cleared from the memory
save	Saves the contents of workspace into mat file
load	Loads the content of an already saved mat file
diary	Creates a log of all the inputs and outputs generated into a an ASCII file

External Interface

MATLAB interacts with data and program external to it. It provides an Application Program Interface (API) to support these external interfaces. The functions supported by API include:

• Calling C or Fortran programs from within MATLAB
• Importing and exporting data to and from MATLAB environment.

MEX-files

These are dynamically linked subroutines provided from C or Fortran source code. While they behave just like M-files and other builtin functions, Mex-files are not platform independent and they have to have a platform- specific extensions.

C and Fortran MEX-files

The include (header files) are located at: /usr/usc/matlab/default/extern/include. Some examples of MEX-files are located at: /usr/usc/matlab/default/extern/examples/mex

Compiling and linking

To compile and link the source files written in C, at the MATLAB prompt, type the command mex. This will create a mexsol file, which will behave exactly like an M-file in MATLAB. You can also combine several object and use libraries while building MEX-file. The full path name for the mex function is: /usr/usc/matlab/default/bin/mex.

Important header files and libraries

mex.h	MEX-file declaration and prototype
mat.h	Mat-file declaration and prototype
engine.h	engine declaration and prototype
matrix.h	basic matrix access methods
libmex	library for building MEX-files
libmat.a	library for MAT-files and engine routines

Notes:

• mex.h, mat.h, engine.h all include matrix.h themselves, so there is no need to include matrix.h explicitly.
• mex.h, mat.h, engine.h all include matrix.h themselves, so there is no need to include matrix.h explicitly.

Basic Plotting and Graphic Functions

plot	Graph of vectors with linear scales for both axes
loglog	Graph with logarithmic scale for both axes
semilogx	Graph with logarithmic scale for x-axis and a linear scale for y-axis
semilogy	Graph with logarithmic scale for y-axis and a linear scale for x-axis
plotyy	Graph with y-tick labels on the left and right side
title	Title of the graph
xlabel	Label of the x-axis
ylabel	Label of the y-axis
gtext	Place text on the graph using the mouse
text	Display text on specific location
grid	Turn the grid on

3-D Graphics

mesh,surf	Surface plot for matrix data
meshc,surfc	Surface plot with contour plot beneath it
meshz	Surface plot with reference plane
pcolor	Flat surface plot (value is proportional only to color)
surfl	Surface plot illuminated from specified direction
surface	Low-level function (on which high-level functions are based)
plot3	The 3-D analog of the plot function

Getting Help With MATLAB

To get general MATLAB help, type help at the MATLAB command prompt to get a list of a help topics. To get help on a specific topic or function, type help at the prompt, replacing with the topic or function you wish to get help on.

MathWorks provides extensive MATLAB documentation online. To access this documentation, go to MATLAB Getting Started

If you have questions regarding this documentation, or are having trouble logging into your account and sourcing the MATLAB setup files, please contact the Customer Support Center at 213-740-5555 or email consult@usc.edu.