Transcript Extending MATLAB    Write your own scripts and/or functions Scripts and functions are plain text files with extension .m (m-files) To execute commands contained in.

Extending MATLAB
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Write your own scripts and/or functions
Scripts and functions are plain text files with
extension .m (m-files)
To execute commands contained in m-files,
MATLAB needs to know where they are!
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store in working directory
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store in any directory, add to MATLAB's path
Reminders
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To check/change working directory
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pwd, cd, ls, dir
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menu bar
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current directory window
To check/modify path
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path
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addpath, rmpath, savepath
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File >> Set Path...
Scripts
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No input/output
Operate on pre-defined workspace variables
and variables defined in script
Variables created during script are saved in
workspace (side effects)
Kind of like macros, relatively inflexible
→ good for executing repeated long/complicated
sequences of commands on same data
How to execute a script
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Save list of commands, variable definitions, etc
in plain text file 'scriptEx.m'
Make sure 'scriptEx.m' is saved in wd, OR, its
directory is added to path
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type 'scriptEx' at command prompt (no quotes)
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Be aware of side effects
Functions
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Basically, scripts that take input and create
some output
Operate on input variables and variables
defined in function
Variables created during function call
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only exist as long as function is running
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can be saved to workspace if defined as output
→ good for performing general tasks with optional
parameters on different datasets
How to call your function (1)
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Write it (we'll get to that), and save as plain text
file 'functionEx.m'
Make sure 'functionEx.m' is saved in wd, OR, its
directory is added to path
Let's assume your function has 2 input
arguments, these could be input data or
parameters to pass to function body
Examples ...
How to call your function (2)
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Arg1 is data stored as workspace variable, Arg2
is file containing other data
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Arg1 is data, Arg2 is desired name of output file
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>> functionEx(x, 'filename.txt')
>> functionEx(x, 'output.txt')
Arg1 is another function, Arg2 is scalar
parameter
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>> functionEx(@func, 1000)
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>> functionEx('func', 1000)
Defining your function
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First line must contain the following
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'function' command
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name(s) of output, if any
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name of function, should be same as name of m-file
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name(s) of input parameters/arguments
function output = userFunc(arg1, arg2)
function [ ] = userFunc(arg1, arg2, arg3)
function [out1, out2] = userFunc(arg1)
What about lines 2,3,4,...?
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Function body can contain anything, as long as
it's a valid MATLAB statement/command
Any text preceded by a % is not executed →
% this is a comment
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If function definition on line 1 is followed by
block of commented lines, comments will be
printed as help file when user types
>>help userFunc
Programming basics
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Loops
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for loop → perform a set of commands for some
predetermined amount of times
while loop → perform set of commands as long as
some condition is met
If-then statements
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if some condition is met → perform set of
commands
else and elseif
For loop
While loop
If statement
File handling
>>help iofun