Lecture 1: Matlab Universe Tom Rebold ENGR 52

Course Overview

The Way the Class Works I lecture for 15 – 20 minutes You do lab for 30 – 40 minutes Labs link to extra Problems online for fast students Everyone turn in a solution to the last problem they solve today HOMEWORK: Bring in 3 Math problems to solve…medium, hard, impossible  We’ll have independent study time

To Buy Matlab Student Version, $100 Can purchase, download online  Link from ENGR196.3 class webpage Bookstore does not stock MATLAB retails for $1600, so it’s a pretty good deal BETTER DEAL: FreeMAT !!  Open source version, powerful, free, legal

Why MATLAB 10x faster compared to other choices:  C++, Fortran, Java  Excel, MathCad, Mathematica, Labview Matlab is a Very High Level Language  Designed for complex numerical calculations  Vast array of Toolboxes for different specialties  Excellent visualization tools  Symbolic math somewhat awkward  Simulink for modelling dynamic systems, 10x faster still

Today’s Agenda MATLAB Overview Working in MATLAB’s Environment Simple calculations, variables

MATLAB’s ENVIRONMENT

Download week1.zip Follow instructions in Lab1  View toolbox demos  Experiment with workspace configuration

Numeric Data At it’s most basic level, Matlab can be used as a simple calculator, by typing in an arithmetic expression and hitting enter. For example, at the command prompt, type: >> 8/10 >>4 * 3 >>8/10 + 4*3 >>9^2 (what does the ^ operator do? )

Arithmetic rules of precedence >> 8 + 3*5 >> 8 + (3*5) >> (8 + 3) * 5 >> 4^2 – 12 >> 8/4*2 >> 8/(4*2) >> 3*4^2 >> (3*4)^2 >>27^(1/3) >> 27^1/3

built in functions Matlab has hundreds of built in functions to do more complicated math  sqrt(9)  log10(1000)  log(10)  pi  cos(pi)  i  exp(i*pi)

Variables Usually we need to hang on to the result of a calculation  We need a way to name memory for storage  Variable--name of a place in memory where information is stored r = 8/10 r s=20*r score = 4 * r + s z = sqrt(1000) z = sqrt(s)

Assignment Operator = means “gets” Translation: MATLAB: r = 8/10 ENGLISH: r “gets” the value 8/10 OK in Math x + 2 = 20 NOT OK IN MATLAB !! (only variable on Left Side)

Expressing Math in MATLAB 2 yx _______________ x-y 3x _______________ 2y

Saving Work in Matlab Script (.m) files You’ll want to build up complex calculations slowly  Try, correct, try again, improve, etc .m Files store your calculations  Can be edited in Matlab  Can be re-executed by typing the file name

Example.m file Volume of a Cylinder. The volume of a cylinder is V=  r2h. A particular cylinder is 15 meters high with a radius of 8 meters. We want to construct another cylinder tank with a volume 20% greater, but with the same height. How large must its radius be? The session follows:  r = 8;  h = 15;  V = pi*r^2*h  V = V + 0.2*V  adds 20% to V  r = sqrt(V/ (pi * h)) Put this in a file called cyl_volume.m to save retyping

Solve some problems! Pick any problem, solve it and print your solution.m file Write name, turn in You may wish to save your class.m files on a USB drive