MATLAB tutorial

1. MATLAB tutorial CIVL 5320 Thomas Ng

2. Getting Started with Matlab • What isMatlab? • MATrixLABoratory • Ahigh-performance language for technical computing • An easy-to-use interactive environment for computation, visualization and programming

3. Input and Output • Interactive: Direct key in command after “>>” • >> help • >> lookforCCChang • 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”

4. Input and Output • 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

5. Exercise • Do the followings • >> help help • >> help lookfor • >> help plot • >> lookfor plot • Put sdof.m and elcen.mat into the current directory • >> sdof • >> whos • >> save temp • >> clear all • >> whos • >> load temp • >> whos • Create a m-file that contains the above commands and run the m-file

6. Basic Operations • 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: %

7. Basic Operations • Some useful commands • >> Clear >> Close • Scalar, vector and matrix • >> A=123 >> a=321% • >> 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)

8. Exercise • Do the followings • >> 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]’

9. Exercise • >> CC=[1 2 3; 4 5 6; 7 8 9] • >> CC=[1:3; 4:6; 7:9] • >> subCC1=CC(1:2, 2:3) % what do youexpect? • >> subCC2=CC(: , 2:3) % what do youexpect? • >> subCC3=CC(1:2, :) % what do youexpect? • >>clear all

10. Basic Operations Matrix operation Element by element operation

11. Special Variables

12. Built-in Functions

13. Exercise • 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’

14. Exercise • >> CC=[1 2; 3 4] • >> det(CC) • >> eye(2) • >> zeros(2,2) • >> DD=[CC zeros(2,2); zeros(2,2) eye(2)]

15. Plotting Figures • Figure control • >> figure(x)% Create/go to figure x • >> clf(x) % Clear figure x • >> close(x) % Close figure x • >> title(‘I love MATLAB’) % Figure caption • Plotting • >> 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

16. Plotting Figures • Plotting control • >> axis([xminxmaxyminymax]) • >> xlabel(‘This is x-axis label’) • >> ylabel(‘This is y-axis label’) • >> text(x, y, ‘This is a label’) % Add text to (x,y)

17. Exercise • Open sdof.m file • Go through the codes • Run sdof.m file • Modify the file • Re-run

18. demo