Advanced MATLAB (for Electrical Engineers) Instructor: Kamran Arshad EE Club, KFUPM 28 March 2004 KFUPM

Advanced MATLAB Course for Electrical Engineers (Kamran Arshad) Course Information Course Destination  Course is designed for non-professionals and engineers who wish to expand his pervious skills in using MATLAB. Prerequisite  Preliminary skills in MATLAB are required for this course. Syllabus  Course contents and syllabus is on the consent of instructor.

Advanced MATLAB Course for Electrical Engineers (Kamran Arshad) Course Syllabus  First Day Introduction to MATLAB, Basics of Matrix Algebra, Iterative Calculations, Graphical Illustration  Second Day Specifically deal with problems of Communication Engineering  Third Day Deal with problems of Digital Signal Processing and Control Theory MINOR MODIFICATIONS MAY TAKE PLACE

Advanced MATLAB Course for Electrical Engineers (Kamran Arshad) What is Matlab?  A software environment for interactive numerical computations  Examples:  Matrix computations and linear algebra  Solving nonlinear equations  Numerical solution of differential equations  Statistics and data analysis  Signal processing  Modelling of dynamical systems  Solving partial differential equations  Simulation of engineering systems

Advanced MATLAB Course for Electrical Engineers (Kamran Arshad) Why should you attend this course?  Matlab used (on a daily basis) in many engineering companies

Advanced MATLAB Course for Electrical Engineers (Kamran Arshad)  Matlab used in many courses at KFUPM 1. EE 370 Communication Engineering 2. EE 380 Control Theory 3. EE 270 Signals and Systems  Image Processing, Digital Signal Processing, and some courses at other departments of university Why should you attend this course? (contd)

Advanced MATLAB Course for Electrical Engineers (Kamran Arshad) Matlab Background  Matlab = Matrix Laboratory  Originally a user interface for numerical linear algebra routines (Lapak/Linpak)  Commercialized 1984 by The Mathworks  Since then heavily extended (defacto-standard)  Higher-level, similar to ‘C’ programming environment; no compiler  2D (rectangular & polar) and 3D display of data, functions, system responses

Advanced MATLAB Course for Electrical Engineers (Kamran Arshad) Iterative Calculations  Matlab is interactive, no need to declare variables  >> 2+3*4/2  >> a=5e-3; b=1; a+b  Most elementary functions and constants are already defined  >> cos(pi)  >> abs(1+i)  >> sin(pi)  Last call gives answer e-016 !?

Advanced MATLAB Course for Electrical Engineers (Kamran Arshad) Variable and Memory Management  Matlab uses double precision (approx. 16 significant digits) >> format long >> format compact (see all other formats by typing help format on command prompt)  All variables are shown with >> who >> whos  Variables can be stored on file >> save filename >> clear >> load filename

Advanced MATLAB Course for Electrical Engineers (Kamran Arshad) The Help System  Search for appropriate function >> lookfor keyword  Rapid help with syntax and function definition >> help function  An advanced hyperlinked help system is launched by >> helpdesk  Complete manuals as PDF files

Advanced MATLAB Course for Electrical Engineers (Kamran Arshad) Some Useful Commands  whos shows the environment  clear removes all variables from memory  clearv1 ez removes variables v1 & ez from memory  clf clears the current figure or graph  clc clears the command window  dir lists current directory  delete fname deletes file named fname  help matlab\general General purpose commands  help matlab\ops Operators and special characters  help matlab\lang Programming language constructs  help matlab\elmat Elementary matrices  help matlab\elfun Elementary math functions To abort type ctrl c

Advanced MATLAB Course for Electrical Engineers (Kamran Arshad) Vectors and Matrices  Vectors (arrays) are defined as  >> v = [1, 2, 4, 5]  >> w = [1; 2; 4; 5]  Matrices (2D arrays) defined similarly  >> A = [1,2,3;4,-5,6;5,-6,7]

Advanced MATLAB Course for Electrical Engineers (Kamran Arshad) Matrix Operators  All common operators are overloaded >> v + 2  Common operators are available >> B = A’ >> A*B >> A+B  Note:  Matlab is case-sensitive A and a are two different variables Transponate conjugates complex entries; avoided by >> B=A.’

Advanced MATLAB Course for Electrical Engineers (Kamran Arshad) Indexing Matrices  Indexing using parentheses >> A(2,3)  Index submatrices using vectors of row and column indices >> A([2 3],[1 2])  Ordering of indices is important! >> B=A([3 2],[2 1]) >> B=[A(3,2),A(3,1); A(2,2);A(2,1)]

Advanced MATLAB Course for Electrical Engineers (Kamran Arshad) Indexing Matrices(Cond)  Index complete row or column using the colon operator >> A(1,:)  Can also add limit index range >> A(1:2,:) >> A([1 2],:)  General notation for colon operator >> v=1:5 >> w=1:2:5

Advanced MATLAB Course for Electrical Engineers (Kamran Arshad) Arithmetic Operations and Precedence OperationAlgebraicMatlab FormScalar additiona + ba + b subtractiona – ba – b multiplicationa x ba * b divisiona ÷ ba / b exponentiation a b a ^ b PrecedenceOperation 1Parenthesis, innermost first. 2Exponentiation, left to right 3Multiplication & division, left to right 4Addition & subtraction, left to right

Advanced MATLAB Course for Electrical Engineers (Kamran Arshad) Precedence - Example  % Compute the area of the trapezoid  » base = 5  » height_1 = 3  » height_2 = 7  » area = 0.5*base*(height_1 + height_2)  % What is the area?  » area = 0.5*base*height_1 + height_2  % What is the area?  % Where are the parentheses assumed?

Advanced MATLAB Course for Electrical Engineers (Kamran Arshad) Matrix Functions  Many elementary matrices predefined >> help elmat; >> I=eye(3)  Elementary functions are often overloaded >> help elmat >> sin(A)  Specialized matrix functions and operators >> As=sqrtm(A) >> As^2 >> A.*A  Note: in general, ”. ” is elementwise operation

Advanced MATLAB Course for Electrical Engineers (Kamran Arshad) Numerical Linear Algebra  Basic numerical linear algebra >> z=[1;2;3]; x=inv(A)*z >> x=A\z  Many standard functions predefined >> det(A) >> rank(A) >> eig(A)  The number of input/output arguments can often be varied >> [V,D]=eig(A)

Advanced MATLAB Course for Electrical Engineers (Kamran Arshad) The programming environment  Matlab can’t tell if identifier is variable or function  >> z=theta;  Matlab searches for identifier in the following order 1. variable in current workspace 2. built-in variable 3. built-in m-file 4. m-file in current directory 5. m-file on search path  Note: m-files can be located in current directory, or in path

Advanced MATLAB Course for Electrical Engineers (Kamran Arshad) Script files  Script-files contain a sequence of Matlab commands  Executed by typing its name >> factscript  Operates on variables in global workspace  Variable n must exist in workspace  Variable y is created (or over-written)  Use comment lines (starting with %) to document file %FACTSCRIPT – Compute n-factorial, n!=1*2*...*n y = prod(1:n); %FACTSCRIPT – Compute n-factorial, n!=1*2*...*n y = prod(1:n); factscript.m

Advanced MATLAB Course for Electrical Engineers (Kamran Arshad) Displaying code and getting help  To list code, use type command  >> type factscript  The help command displays first consecutive comment lines  >> help factscript

Advanced MATLAB Course for Electrical Engineers (Kamran Arshad) Functions  Functions describe subprograms  Take inputs, generate outputs  Have local variables (invisible in global workspace) [output_arguments]= function_name(input_arguments)  % Comment lines  function [z]=factfun(n) % FACTFUN – Compute factorial % Z=FACTFUN(N) z = prod(1:n); function [z]=factfun(n) % FACTFUN – Compute factorial % Z=FACTFUN(N) z = prod(1:n); factfun.m

Advanced MATLAB Course for Electrical Engineers (Kamran Arshad) Scripts or function: when use what?  Functions  Take inputs, generate outputs, have internal variables  Solve general problem for arbitrary parameters  Scripts  Operate on global workspace  Document work, design experiment or test  Solve a very specific problem once % FACTTEST – Test factfun N=50; y=factfun(N); % FACTTEST – Test factfun N=50; y=factfun(N); facttest.m

Advanced MATLAB Course for Electrical Engineers (Kamran Arshad) Flow control - selection  The if-elseif-else construction if elseif else end if height>170 disp(’tall’) elseif height<150 disp(’small’) else disp(’average’) end if height>170 disp(’tall’) elseif height<150 disp(’small’) else disp(’average’) end

Advanced MATLAB Course for Electrical Engineers (Kamran Arshad) Logical expressions  Relational operators (compare arrays of same sizes) ==(equal to)~= (not equal) (greater than)>= (greater than or equal to)  Logical operators (combinations of relational operators) &(and) |(or) ~(not)  Logical functions xor isempty any all if (x>=0) & (x<=10) disp(‘x is in range [0,10]’) else disp(‘x is out of range’) end if (x>=0) & (x<=10) disp(‘x is in range [0,10]’) else disp(‘x is out of range’) end

Advanced MATLAB Course for Electrical Engineers (Kamran Arshad) Flow control - repetition  Repeats a code segment a fixed number of times for index= end The are executed repeatedly. At each iteration, the variable index is assigned a new value from. for k=1:12 kfac=prod(1:k); disp([num2str(k),’ ‘,num2str(kfac)]) end

Advanced MATLAB Course for Electrical Engineers (Kamran Arshad) Example – selection and repetition function y=fact(n) % FACT – Display factorials of integers 1..n if nargin < 1 error(’No input argument assigned’) elseif n < 0 error(’Input must be non-negative’) elseif abs(n-round(n)) > eps error(’Input must be an integer’) end for k=1:n kfac=prod(1:k); disp([num2str(k),’ ’,num2str(kfac)]) y(k)=kfac; end; function y=fact(n) % FACT – Display factorials of integers 1..n if nargin < 1 error(’No input argument assigned’) elseif n < 0 error(’Input must be non-negative’) elseif abs(n-round(n)) > eps error(’Input must be an integer’) end for k=1:n kfac=prod(1:k); disp([num2str(k),’ ’,num2str(kfac)]) y(k)=kfac; end; fact.m

Advanced MATLAB Course for Electrical Engineers (Kamran Arshad) Flow control – conditional repetition  while-loops are executed repeatedly as long as the evaluates to true while end k=1; while prod(1:k)~=Inf, k=k+1; end disp([‘Largest factorial in Matlab:’,num2str(k- 1)]); k=1; while prod(1:k)~=Inf, k=k+1; end disp([‘Largest factorial in Matlab:’,num2str(k- 1)]);

Advanced MATLAB Course for Electrical Engineers (Kamran Arshad) Programming tips and tricks  Programming style has huge influence on program speed! tic; X=-250:0.1:250; for ii=1:length(x) if x(ii)>=0, s(ii)=sqrt(x(ii)); else s(ii)=0; end; toc tic; X=-250:0.1:250; for ii=1:length(x) if x(ii)>=0, s(ii)=sqrt(x(ii)); else s(ii)=0; end; toc tic x=-250:0.1:250; s=sqrt(x); s(x<0)=0; toc; tic x=-250:0.1:250; s=sqrt(x); s(x<0)=0; toc; slow.m fast.m Loops are slow: Replace loops by vector operations!

Advanced MATLAB Course for Electrical Engineers (Kamran Arshad) MATLAB Graphics  MATLAB also provides a powerful set of graphics commands to create and manipulate graphics  Many commands can be entered from the Figure window  Advanced commands must be entered from the Command window or a script

Advanced MATLAB Course for Electrical Engineers (Kamran Arshad) Graphics  Visualization of vector data is available >> x=-pi:0.1:pi; y=sin(x); >> plot(x,y) >> plot(x,y,’s-’) >> xlabel(’x’); ylabel(’y=sin(x)’);  Can change plot properties in Figure menu, >> h=plot(x,y); set(h, ’LineWidth’, 4);  Many other plot functions available >> v=1:4; pie(v)

Advanced MATLAB Course for Electrical Engineers (Kamran Arshad) Graphics  Three-dimensional graphics >> A = zeros(32); >> A(14:16,14:16) = ones(3); >> F=abs(fft2(A)); >> subplot(211),mesh(A); >> subplot(212),mesh(F); >> rotate3d on % Turn on mouse based movement  Several other plot functions available >> surfl(F)  Can change lightning and material properties >> cameramenu >> material metal

Advanced MATLAB Course for Electrical Engineers (Kamran Arshad) Practice Using Matlab  MatLab  >>numerator = x^3 - 2*x^ ;  >>denominator = x^ x – 3.14;  >>f = numerator / denominator  Advice  Use several statements … easier to debug … will save you time.  Use parenthesis … do not rely on precedence rules

Advanced MATLAB Course for Electrical Engineers (Kamran Arshad) Practice Using Matlab  Calculate roots of quadratic equation.  Advice  Take as input the values of a, b and c.  Apply check for different type of roots, and calculate roots.  Print out the values of roots on the screen !!!

Advanced MATLAB Course for Electrical Engineers (Kamran Arshad) Summary Lecture  Understand the MATLAB environment  Understand various commands of MTALAB  Run small MATLAB segments  Graph data  Summary Action Items  Review the lecture  Record what you learned and how this relates to your Learning Objectives for this class  Explore MATLAB.  Practice commands  Come prepared to ask questions about MATLAB

Advanced MATLAB Course for Electrical Engineers (Kamran Arshad)