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 m-files, MATLAB needs to know where they are! store in working directory store in any directory, add to MATLAB's path

To check/change working directory pwd, cd, ls, dir menu bar current directory window To check/modify path path addpath, rmpath, savepath File >> Set Path... Reminders

Scripts 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 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 type 'scriptEx' at command prompt (no quotes) Be aware of side effects

Functions Basically, scripts that take input and create some output Operate on input variables and variables defined in function Variables created during function call only exist as long as function is running 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) 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) Arg1 is data stored as workspace variable, Arg2 is file containing other data >> functionEx(x, 'filename.txt') Arg1 is data, Arg2 is desired name of output file >> functionEx(x, 'output.txt') Arg1 is another function, Arg2 is scalar parameter >> 1000) >> functionEx('func', 1000)

Defining your function First line must contain the following 'function' command name(s) of output, if any name of function, should be same as name of m-file 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,...? 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 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 Loops 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 if some condition is met → perform set of commands else and elseif

For loop

While loop

If statement

File handling >>help iofun