Beyond the Basics - Basics of MATLAB and Beyond - page 179

38.3 Debugging
matlab has a suite of debugging commands. A list of them can be
obtained by typing help debug :

dbstop Set breakpoint dbstatus List all breakpoints

dbclear Remove breakpoint

Execute one or more

dbstep

dbcont Resume execution

lines

dbdown Change local

List M-file with

dbtype

workspace context line numbers

Change local Enable mex file

dbup dbmex

workspace context debugging

dbstack List who called whom dbquit Quit debug mode

Other commands that are useful when debugging code are

keyboard Put this command in a function and the function will stop at
that point and return control to the command window, but within
the function's environment. This means that variables within the
function can be accessed for printing out, plotting, etc. The com-
mand window prompt changes to K>> while the keyboard function
is in effect. You can resume execution of the function by typing
the character sequence r , e , t , u , r , and n at the K>> prompt,

echo Use the echo command to display each line of a script or function
as it is executed.

diary The diary command is used when you want to save a copy of
everything that appears in the command window, both what you
type and what matlab types, in a file.

more The more command stops the screen from scrolling each time it
fills with text. You can advance the screen one page at a time by
pressing the space bar, or one line at a time by pressing the return
key. If you press q when the screen is stopped, the current display
will end at that point.

38.4 Profiler

The profile command measures the time taken to execute each line of
code. Let us use it to examine the performance of the following code to
produce an image of the Mandelbrot set (see companion software):

function mandelbrot
% MANDEL.M Produces a plot of the famous Mandelbrot set.
%see: http://eulero.ing.unibo.it/~strumia/Mand.html
% The generator is z = z^2+z0. Try changing the parameters:
N = 400;