Matlab Introduction

Matlab Introduction Tim Brunner Daniel Moore

What is Matlab?
MAT rix LAB oratory
Computing environment and programming language allowing for powerful numerical / image analysis and manipulation
basic data element is an array that does not require dimensioning
It allows you to solve many technical computing problems, especially those with matrix and vector formulations, fairly quickly

Why use Matlab?
Huge library of mathematical functions and algorithms
Fast implementation of vector/matrix operations
Powerful visualizations (when used properly)

Sample Matlab Screen Command Window: Insert Matlab statements at the prompt Command History Current Directory Script Editor

Useful documentation (Seriously) For documentation on a particular command just type `doc <command>` at the prompt … Or use the help menu bar

Matrix and Vector Algebra
MATLAB is based on matrix and vector algebra
Even scalars are treated as 1x1 matrices
This means you have to be careful when using operators on data
Rule of thumb: functions (like sin(), cos(), etc.) act on each individual element; operators perform matrix operations
Use dot operator notation to operate on individual elements (.*, ./)

Graphing
Matlab can make a large variety of graphs
User has a large degree of control over what can appear on the graph
Graph can be made from the Matlab command line or by using the plot tools GUI
Plot, quiver, pcolor, many plot options
Many color schemes

Importing Data
Matlab can import data from a variety of sources
Can import using the Import Data tool or programmatically
XLSRead is good for importing .xls files
[Numeric, txt, raw]=xlsread(File, Sheet, Range)

Basic Programming
M-files store Matlab command lines
Can be run from the command line
When run, they execute all of the commands contained in it as if you had typed these into a command window (like a keyboard macro)
M-files can contain scripts or functions (or both or multiple functions)
Function variables are local to that function
Scripts only operate on variables that are hard coded into their m-file

Some simple commands
Some basic loops
for i=1:10 … end
while(i<10) … end
if (a>10) … elseif (a<5) … else … end
switch a case 1 … case 2 … case 3 … … otherwise … end
Formatting
% comments out a line
%% can help divide a section

File directory structure
Recommend that user m-files go in a MATLAB directory within “My Documents”
Use subdirectories for various projects
Put directories into matlab “path” allows calling functions from any directory

Working “live” on command line
From program, go “live” with keyboard command
“ who” command lists currently defined variables
Commands work – same as in program
Live graphs, or modifications to existing graphs
History of command input, accessed by arrow keys

Fitting data
Data displayed in a plot can be fit to polynomials
Built in to plot window - tools/basic fitting
Also can use matrix ‘backslash’ operator

Basic Programming
M-files

Additional resources
Matlab tutorial (pdf file)
Matlab built-in demos (in help)
Demos available on-line
http://www.mathworks.com/academia/student_center/tutorials/launchpad.html
User contribution repositories
On mathworks web site

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Matlab Introduction

by Daniel Moore

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