CIVL 5320
Thomas Ng
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 What is Matlab?
 MATrix LABoratory
 A high-performance language for technical computing
 An easy-to-use interactive environment for computation,
visualization and programming
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 Interactive: Direct key in command after “>>”
 >> help
 >> lookfor CCChang
 Off-line: Put all commands into a m-file (name.m)
and execute the file as follows
 >> name (without suffix .m)
 All commands in the file will be executed sequentially
 The m-file has to be in the current directory or
directories set by “pathtool”
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 mat-file (name.mat): Contains pre-defined variables,
vectors and matrices
 >> save name
Save all variables into a file called name.mat
 >> save name CCChang is wonderful
Save variables, vectors or matrices “CCChang”, “is” and
“wonderful” into a file called name.mat
 >> load name
Load all variables in the name.mat to the MATLAB registry
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 Do the followings
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>> help help
>> help lookfor
>> help plot
>> lookfor plot
 Put sdof.m and elcen.mat into the current directory
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>> sdof
>> whos
>> save temp
>> clear all
>> whos
>> load temp
>> whos
 Create a m-file that contains the above commands and run the
m-file
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 Sequence of operations
 >> CCChang
 Is CCChang a variable? If not, next
 Is CCChang a built-in function? If not, next
 Is CCChang a m-file? If not, next
 ??? Undefined function or variable 'CCChang‘
 Some useful commands
 Interrupting running the program: Ctrl+c
 Long command: …
>> x=sin(1)+1+cos(2)+sin(2)+ sin(2)+...
sin(4)+ sin(5)+ sin(6)+ sin(7)
 Suppress echo: ;
 Comment: %
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 Some useful commands
 >> Clear
>> Close
 Scalar, vector and matrix
>> a=321 % A  a
>> Rowvector = [12 14 63]
>> Colvector= [13; 45; -2]
>> Matrix= [1 2 3; 4 5 6; 7 8 9]
>> sub_matrix= Matrix( 1:2 , 2:3)
 >> A=123
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 Do the followings
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>> A=123
>> A=123
%This is fun!
>> A=123;
>> x=sin(1)+1+cos(2)+sin(2)+ sin(2)+...
sin(4)+ sin(5)+ sin(6)+ sin(7)
>> ColA=[1 ; 2 ; 3]
>> RowA=[1 2 3]
>> GuessA=[1:10]
>> GuessB=[1:3:10]
>> GuessC=[1:10]’
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 >> CC=[1 2 3; 4 5 6; 7 8 9]
 >> CC=[1:3; 4:6; 7:9]
 >> subCC1=CC(1:2, 2:3)
 >> subCC2=CC(: , 2:3)
 >> subCC3=CC(1:2, :)
% what do you expect?
% what do you expect?
% what do you expect?
 >> clear all
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Matrix
operation
Power
Multiplication
Division
or
NOTE:
^ or .^ a^b
* or .* a*b
/ or ./ a/b
\ or .\ b\a
56/8 = 8\56
- (unary) + (unary)
Addition
+
Subtraction
Assignment
=
or
or
or
or
a.^b
a.*b
a./b
b.\a
Element by element
operation
a + b
a - b
a = b
(assign b to a)
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ans
pi
inf
NaN
i and j
eps
realmin
realmax
Default variable name for results
Value of 
Not a number e.g. 0/0
i = j = 1
Smallest incremental number
The smallest usable positive real number
The largest usable positive real number
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Command
Description
eye
Identity matrix
zeros
Zeros array
norm
Norm of vector or matrix
det
Matrix determinant
eig
Eigenvalues and eigenvectors
lsim
Simulate response of LTI models
for … end
Repeat statements (do loop)
demo
Run demonstrations
Many many more!
Toolboxes contain specialized commands
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 Do the followings
 >> RowA=[1 2 3]; ColA=[1 ; 2 ; 3];
 >> RowA*ColA
 >> ColA*RowA
 >> ColA.*RowA
 >> ColA.*RowA’
 >> RowA.*ColA
 >> RowA.*ColA’
 >> RowA./ColA
 >> RowA./ColA’
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 >> CC=[1 2; 3 4]
 >> det(CC)
 >> eye(2)
 >> zeros(2,2)
 >> DD=[CC zeros(2,2); zeros(2,2) eye(2)]
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 Figure control
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>> figure(x)
% Create/go to figure x
>> clf(x)
% Clear figure x
>> close(x)
% Close figure x
>> title(‘I love MATLAB’)
% Figure caption
 Plotting
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>> plot(y)
% Plot y versus index
>> plot(x,y)
% Plot y versus x
>> semilogx(x,y)
>> semilogy(x,y)
>> loglog(x,y)
>> plot3(x,y,z)
>> subplot(m,n,p)
% Create tiled plots
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 Plotting control
 >> axis([xmin xmax ymin ymax])
 >> xlabel(‘This is x-axis label’)
 >> ylabel(‘This is y-axis label’)
 >> text(x, y, ‘This is a label’) % Add text to (x,y)
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 Open sdof.m file
 Go through the codes
 Run sdof.m file
 Modify the file
 Re-run
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