DEBUGGING Matlab .m files
MATLAB provides a debugging facility that allows you to stop at
specific points in your .m files, examine the workspace and
step through execution of your code. For example, while developing
a function ops.m, an error occurs. Matlab will give an error message
similar to:
??? Error using ==> ones
Too many input arguments.
Error in ==> /afs/athena.mit.edu/software/vizdev/matlab/ops.m
On line 10 ==> A = ones(n,n,n);
The first 2 lines explain the error, and the next two give the
location of the error. To use the debugging facility to determine
what is happening, you start with the "dbstop" command. This command
provides a number of options for stopping execution of a Matlab
function. A particularly useful option is
>> dbstop if error
This causes a stop in any M-file function causing a run-time error.
Then just run the Matlab command. In this case
>> ops(5)
Execution will stop at the point where the error occurs, and you will get the
Matlab prompt back so that you can examine variables or step through
execution from that point. In the example:
>> ops(5)
10 A = ones(n,n,n);
K>>
The command "dbstep" allows you to step through execution one line
at a time. You can continue execution with the "dbcont" command.
To exit debug mode, type "dbquit".
For more information, see the Matlab help for the following topics:
debug, dbstop, dbclear, dbcont, dbdown, dbstack, dbstatus
dbstep, dbtype, dbup, dbquit
last updated: 7/13/95
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