Introduction To MatlabClass 1Instructors: Hristiyan (Chris) Kourtevand Xiaotao Su, PhD

Double click the matlab iconWhen prompted click Skip, then type:

mkdir C:/MatlabClass/YourLastNamecd C:/MatlabClass/YourLastName

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IntroductionAsk Questions!Slides, notes, assignments, and other info will be at:http://ruccs.rutgers.edu/matlab_course/

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SetupClick Matlab mkdir C:/MatlabClass/YourLastNamecd C:/MatlabClass/YourLastName

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ProgrammingMatlab has its own programming languageWhat is a program?A series of instructions that the computer followsAlso referred to as Code or a Script

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Two Options For Where To Issue Commands/InstructionsIn the command windowIn a script (program) executed by the command window.

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Hello WorldAt the command prompt type:my_var = hello world;

And press ENTER.Note: The _ character is the shifted dash SHIFT + -

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Hello World my_var = hello world;

Variable NameSingle quotes denote character stringSemi-colon is so you dont output the result to the screen.

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Variables my_var = hello world;

Variable Namemy_varhello worldnum_apples = 7num_apples7num_oranges = 3.53.5num_oranges

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MemoryEach of the values are stored in memory associated with the variable nameThe who command will list the current variables in memoryTyping my_var will return the value of that variableYour computers memory

Var NameValuemy_varhello worldnum_apples7num_oranges3.5subject_namejohn smith

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Setting valuesAs you have seen you set the value of a variable with the = signYou can also set a variable equal to another variable or the output of an operation on a variable.

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Setting valuesnew_var = my_varfruit = num_apples + num_orangesthird_character = my_var(3)this is 7this is 3.5this is now 10.5num_apples = 6what is the value of fruit now?

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Changing around strings

Typing my_var(3) will return l

my_var(3) = my_var(1) Now what is the value of my_var?

my_var is currently hello world

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Calling FunctionsA function is a program that you call on to do some sort of actionlength(hello world)length(my_var)disp(my_var)

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Nesting Functionsdisp(length(my_var))What happens here?disp( length(hello world) )disp(11)11

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Your first programWhat is pseudo-code and why we need itTyping commands one at a time isnt very efficient, especially when you want to do the same ones repeatedlyso we create a program to do itThis program will be called mix_strings

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CommentsComments are descriptions of what is happening in your code. They are need to follow what is happening for debugging purposesAt the beginning of a script you put in a type of comment called a header

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% mix_strings.m % % Displays the string hello world % Then scrambles letters in that string and% displays the scrambled string% % written by XYZ 3/6/2005 % symbol makes this line commented out This means that the computer will ignore these linesName of fileDescription: What does this file do?Who wrote it and when?These lines arent for the computer, they are for you

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So what is the header good for?Save the file At the command line type:help mix_strings

All matlab programs have headers. Find out information on disp, pause, and length

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What else?lookfor can be used to search for programs that have certain words in their headers.lookfor stringlookfor random

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Back to the programclear all;my_var = hello world;mixstr = my_var;mixstr(3) = my_var(1);mixstr(1) = my_var(3);disp(mixstr);

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Now run itIn the command window:mix_strings

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loopsUsed to repeat the same chunk of code many times

for i=1:5disp(i)end;

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mix_strings2.mclear all;my_var = hello world; mixstr = xxxxxxxxxx;for i=1:length(my_var)mixstr(i) = my_var(i);end;

disp(mixstr)

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rand and ceilrand will create a random number from 0 to 1ceil will round up any number to the next integerTogether you can create random integers ceil(rand*7)

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task 1Replace each x in mixstr with a random character from my_var.Start with the first x, then the second x

hello worldxxxxxxxxxxxxxResult could be -> wdolhrdlhlwe

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% mix_strings3.m%%Displays the string 'hello world, then scrambles letters in that string%and displays the scrambled string%% written by Chris Kourtev 7/12/2010 clear all;my_var = 'hello world'; mixstr = 'xxxxxxxxxxxxx'; disp(my_var);for i = 1:length(mixstr) mixstr(i) = my_var(ceil(rand*length(my_var)));end;

disp(mixstr);

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Vectors & MatrixesA string is a list of charactersYou can also have lists of numbers using vectors and matrixesvect = [1, 2, 5, 6, 3] mat = [1, 5, 3; 2, 1, 5; 7, 9, 0]mat = [1, 5, 3; 2, 1, 5; 7, 9, 0]

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Vectors & Matrixesvect = [1, 2, 5, 6, 3] mat = [1, 5, 3; 2, 1, 5; 7, 9, 0]Vectmatmat = [1, 5, 3; 2, 1, 5; 7, 9, 0]note: vectors are basically 1 dimensional matrixes

12563

153215790

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Getting Values out of Vectors & MatrixesVectmatvect(3) returns 5mat(3,1) returns 7Note: to get a cell you use (ROW, COLUMN)

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vector as a 1D matrixvect = [1; 2; 3]vect2 = vect

123

123

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transposing matmat =mat = if you set t_mat = matt_mat(3, 1) is equal to mat(1,3)

Rows and columns are swapped when you transpose a matrix

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127519350

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performing operationsvect + 3vect + vectvect - 3vect + [5, 4, 3]mat+mat

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multiply and divideDont forget to put a dot before multiplication and division symbolsvect.*3mat.*0.5vect./2vect2 = [2; 2; 4]vect.*vect2vect./vect2

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task 2Create a 6(rows)x4(columns) matrix filled with random integer values between 1 and 20Create a zeroes matrix of the same dimensionsReplace each zero with a random number from the other matrix (as we did in the mix_strings program)Display each value in the new mixed matrix

Hint 1: You will need to use nested loopsHint 2: Look up how to use the zeros command

** Advanced task: Design your program so that it can work with matrices of any dimension just by changing the number of rows and column. Hint: Look up the size command