MATH 493 Introduction to MATLAB

MATLAB MATLAB is run as an interactive program You type a command, MATLAB responds with an answer; repeat MATLAB processing is based largely on array and matrix manipulations

MATLAB Interface

Basic Usage Enter simple calculations at the command prompt Define variables at the command prompt Use cursor keys to revisit previous commands Use first letters and cursor keys for more control

Editor Use File/New/Blank M-file to create a script file store a sequence of commands for later use editor does automatic highlighting necessary for anything more than toy examples

Further Commands Standard mathematical functions are built in: cos, sin, log, log10, exp Suppress output with semi-colon User variable names should be different from built-in functions, variables File/Clear Workspace (or type ‘clear’) to clear all variables

Matrices and MATLAB (Nearly) all MATLAB variables are matrices scalars are 1x1 matrices vectors are 1xn or nx1 matrices ‘size’ function gives dimensions of a matrix

Manually Creating Matrices Use square brackets v = [1 3 10] Semi-colons separate rows v = [1; 3; 10] Sometimes easier to write using matrix transpose, ’. Compare v = [1 3 10]’

Functions for Creating Matrices 1 Colon operator 1:5 - same as [1 2 3 4 5] 1:0.1:2 - counts by 0.1 from 1 to 2 linspace linspace(10,50, 1000) - counts from 10 to 50 using 1000 points linspace(10,50) - counts from 10 to 50 using (default) 100 points. Often used for quick graphs

Functions for Creating Matrices 2 ones ones(3) - creates 3x3 matrix of ones ones(4,1) - creates 4x1 vector of ones zeros zeros(3) - creates 3x3 matrix of zeros zeros(4,5) - creates 4x5 matrix of zeros eye - (for “Identity”) eye(3) - creates 3x3 identity matrix

This is not C Many MATLAB functions can take in single arguments or matrices Using a matrix is often faster and more clear Plotting example - graph of cosine x = linspace(0, 6*pi) y = cos(x) plot(x, y)

Plot Command Requirements ‘plot’ will generate an x vs y plot when given two equal-length vectors The plot will appear in a new window There are many plotting options; some are included in the activities

Matrix Problems! Try the following plot of a quadratic x = linspace(-2, 2) y = x^2 plot(x, y) Very common problem in course! x^2 means…. x.^2 means….

Continuing Try the exercises on the sheet. Look at the output each time to make sure you understand what each command is doing!