MATLAB – Basic For Loops Topics Covered: Loops in MATLAB - To repeat code - To access elements of an array Instructor notes: This set of slides covers loops, in particular the for-end loop. Also covered is the break command, which allows a program to jump out of a loop prior to reaching the terminal value of the loop counter. Instructional objectives: Acquire advanced programming concepts including programming using loops Use loops (for-end) and break statements in MATLAB for programming MATLAB - 9

Loops in MatLab What is a Loop ? A loop allows a group of commands in a program to be repeated. Each repetition of the loop is called a pass. Either the number of passes can be fixed. Or the loop can be terminated after some condition is satisfied. Instructor notes: This slide is fairly straightforward. Looping causes a group of commands to be executed repeatedly before moving on to the commands that follow the loop. A loop has a beginning statement, a statement or group of statements that make up its body, and an ending statement. Each time program execution moves through the loop it is called a pass. The number of passes through a loop can be set to some fixed amount, or the looping can be set to continue until a specified condition is reached. It is very likely, and quite possible, that all of the variables used by a loop will reach new values for each pass. We’re talking about the first case today (simple use of a fixed number of passes). MATLAB - 9

Examples of basic for–end Loops for k = 1:3 disp(k) end X=[5, 10, 15, 20]; for i = 1: length(X) disp(X(i)) end Output: 1 2 3 Output: 5 10 15 20 Instructor Notes: These 2 small examples give the essence of the for-end command. The students should type these as programs and then run them to have a feel of how the commands work. MATLAB - 9

for–end loops with vectors Create the vector v = [2 4 6 8]. Calculate and print the square of each element. Output: vs = 4 4 16 4 16 36 4 16 36 64 Program: v = [2 4 6 8] ; for k = 1 : 4 vs(k) = v(k)^2 end Instructor notes: This example introduces the student of going through a vector element by element. Very important that the students understand the addressing of vectors using the for-end loop. Note how the output array is being created one element at a time by the computer. MATLAB - 9

Calculate the factorial of 5 What is a factorial? http://education-portal.com/academy/lesson/how-to-evaluate-factorials.htm l If n=5 and x=1, you continue up to 5 x=x * i 1*1=1 1*2=2 2*3=6 6*4=24 24*5=120 Now, let’s try to have Matlab calculate the factorial of 5.. Presentation Short Title

Additional basic for-end loop example clc clear %This script file calculates the factorial of a number %declare the number you wish to calculate the factorial for n=5; %calculate factorial using a for loop x=1; for i=1:n x=x*i; end fprintf('The factorial of %i is %i\n',n,x)

Matlab Tip of the Day – Dividing your code into Sections Helps focus on one section of the script file Reduces overall computation time Easy to identify errors Helps create awesome published documents  Simple to use All you need is %% (two comment characters or double percent)

Using %% - The Steps Start first code section with %% Write the code for the first section Use %% again to start the next section and so on To run only a particular section Select particular section (by clicking anywhere in the section) Press Ctrl+Enter To run overall code or to publish – same as before