Challenges

During the workshop, activities are provided so that you can engage and test out the content shown for yourself. These are referred to as challenges.

1 Getting Started

1.1 Using MATLAB as a Calculator

Use the MATLAB command prompt to perform the following operations:

• 15 - 21

• 42 x 6

• 7 ÷ 2

• 8 ÷ 2(2 + 2)

Answer the following questions:

• What happens in the Workspace each time you enter a new command?

• How can you 'recall' a previous command if you want to edit it?

• Which order of operations does MATLAB use: BODMAS (Brackets, Order, Division, Multiplication, Addition, Subtraction) or PEMDAS (Parentheses, Exponents, Multiplication, Division, Addition, Subtraction)?

1.2 Saving your work

• Create a folder called "Workshop" and set it as the current working directory.

• Inside your new folder, create a script called "workshop_script". You can use this script to take notes and work through the rest of the challenges.

Hint: for information on Live scripts, visit https://au.mathworks.com/help/matlab/matlab_prog/what-is-a-live-script-or-function.html

2 Variables

2.1 The magic number

• Assign any integer number value to a variable called x

• Create a new variable y which is the sum of x and the number one larger than x

• Now create z starting with y add 9 and divide by 2.

• Then subtract x and multiply by 20.

• What did you get as the final value of z?

2.2 The Workspace

• Save your Workspace: save filename.mat, where filename is any name you choose.

• Clear your Workspace: clear

• Load a previous Workspace: load filename.mat

Hint: To save only one variable, x, use: >> save filename.mat x and to clear only one variable, x, use: >> clear x

When you load a Workspace, this won't clear existing variables in your Workspace; it will add to your existing Workspace.

2.3 Extension: What's in a name

• Enter your name as a string: name1.

• Create another variable, name2, and enter someone else's name.

• Try adding the strings together like we did with numbers earlier. What happens?

3 Vectors and matrices

3.1 Vectors and matrices

• Define the matrix M and row vector p shown below:
• Create a column vector called ages which contains the ages of three people: age1, age2 and age3.

• What is the size of each of these arrays?

Hint: You can check the size of a variable x, on MATLAB using the function size(x)

3.2 Random arrays

• Create a row vector which starts at 7 and ends at 19, counting up by 3.

• Create a row vector which starts at 10 and ends at 0, counting down by 2.

• Create a column vector of five 1s.

• Create a size 3x3 matrix array of random numbers.

Hint: To get random numbers in MATLAB you will need to use the rand() function. Use 'Search Documentation' in the top right corner to learn aboutrand

3.3 Indexing

• Define the matrix M and row vector p shown below:
• Extract the second column of M as a column vector called col2.

• Using indexing on p, let q be another row vector with the elements of p in reverse (that is, you should get q = [2 14 5 9 2 17]).

• Use assignment (=) to edit p to replace the second and last elements with 3 (you should get: [17 3 9 5 14 3]).

• Use the keyword end to get the second-last element of p.

4 Array Operations

4.1 Operation matrix

• The following array contains the average highest (column 1) and average lowest (column 2) temperatures (°F) in Los Angeles for each month in the calendar year: F = [67, 51; 67, 51; 67, 51; 69, 53; 70, 56; 73, 58; 77, 62; 79, 62; 78, 62; 75, 59; 71, 55; 67, 51]. Convert these temperatures to °C using this formula: °C = (°F - 32) x 5 / 9

• Define the column vector a = [3; 1; 2] and the matrix A = [6, 2, 6; 10, 4, 8]. Multiply both of these arrays together, noting that there is only one way to do this. What is the size of the result?

Hint: Recall you can check the size of a variable using the function size()

4.2 Extension

• Transpose the vector a = [3; 1; 2] from the previous challenge to create a_transpose. Now try again to multiply the result with A

• Find the determinant and inverse of G = [1, 3; 4, -1].