Introduction to MATLAB

Timothy FicarraNSF GK-12 Fellow

Vibes and Waves in ActionComputer Architecture and Network Systems Lab

University of Massachusetts Lowell

Presented to two Senior Physics Classes, Lowell High School11/3/09

12/16/09

What is MATLAB?

MATLAB is a software product.Useful for– 2D-3D plotting – Computation/calculation– Prototyping

(prototype: an experimental model)– Creating models and simulations– Algorithms

(algorithm: step-by-step procedure to solve a problem)Makes it easier when calculations are on big sets of numbers.Launch Matlab– Q:/MATLAB/R2009a

MATLAB DesktopCommand Window: a big calculator

Workspace

Command History

Details

CurrentDirectory

Matlab CalculationsBasic operations: +,-,/,*Try:5+46-5+4*3 Question: Does Matlab follow the order of operations?sqrt(121)semicolon (;) stops the output displaysqrt(10); -> will not display the result.abs(-10)2^22^3

Question: What operation is ^ ?

Variables/Numbers

Variable is a place holder for numbers.Example :a = 20.2b = 10.13*a+bList– Matlab allows us to perform operations on list of

numbers. List of number -> an array

– One way to create a list of numbers:T=begin:interval:endExp: t=300:10:350. Question: What are the values of t?

– operations on listExp: 2*T , T+T

Generating Plots

Plot two variables– x=1:1:8; y=50:5:85;– plot(x,y)

Add labels and titles– xlabel(‘Time of the day (hr)’)– ylabel(‘Temperature (f)’)– title(‘Change of temperature during a day’)

Formulas

Formulas are equations. They express information symbolically. Symbols of a formula are variables, which represent an entity.Exp: F=maF: force, m: mass, a: acceleration

Formula Exercise

Celsius/Fahrenheit conversion formula:Celsius = (5/9)*(Fahrenheit – 32)

Exercise:Can you plot the Celsius-Fahrenheit for the

range of -30 to 120 Fahrenheit degrees?

ArraysArray is a space holder for a set of variables.Arrays can be multi-dimensional.– 2D array is a matrix.

Our focus today is on 1D arrays– To enter values for an array:

X=[1,4,2,7,10,3,4,]– You can apply operations on arrays.

Y=X*2– To reach to an element of array

X(N), where N is element index numberexp: X(4)

Measures of Central Tendency

X=[1,4,2,7,10,3,4,]Our sorted data : 1 2 3 4 4 7 10

Matlab functions:– mean(X)– median(X)– mode(X)– range(X)

Total rain fall in Grand Canyoninches

– 1999 16.5 – 2000 15.2– 2001 16.8– 2002 4.2– 2003 17.0– 2004 15.9– 2005 17.1– 2006 14.9– 2007 17.1

2008 16 5

Create an array for rain fall, and plot it. Compute mean, median, mode, range

Outlier?

To eliminate the outlier:X(4)=[ ]X = 16.5 15.2 16.8 17.0 15.9 17.1

14.917.1 16.5

mean(X) = 16.25mode(X) = 16.5median(X) = 16.5range(X) = 2.2