Foundations of computer programming in MATLAB

Expressions

Let’s launch MATLAB and try it out! The Command Window should have a command prompt >>, which is begging for us to enter something. This something is called an expression. Expressions can be something as simple as a number, say 5. If we enter this, and press the return (or enter) key, we should see the following occur.

>> 5
ans = 
     5

What just happened? The interpreter read the expression 5, evaluated it, then printed it.

Let’s have the interpreter do some arithmetic for us.

>> 7 - 5
ans = 
     2

Pretty much what you would expect. But there’s something new here: an operation was performed. This operation was indicated by the - operator, which subtracts the second number from the first. The numbers 7 and 5 are called the operands.

More complex expressions can be evaluated, as well. Parentheses () group expressions to created a nested expression. Here is an example.

>> (3 + 5) - (8/(3 + 1))
ans = 
     6

Exercises

Evaluate the following expressions.

• 2^7
• 2*53
• 2 * 53
• 'hello'
• [1, 2, 3]

Assignment

We can store the output of the evaluation of an expression by assigning it to a variable name.

When we are working in the MATLAB Command Window, assignments are saved in the Workspace. We can assign several variables, then recall them by name.

Example

Let’s store some variables and reuse them.

x = 3;
y = 5;
z = x*y;
disp(z)

Exercise

Store the following variables in a Workspace.

a = 2^3;
B = 78 - 32;
total_number_of_people = 5;
costume = 'duck';
Mask = 'jason';

Now, complete the following tasks.

• Assign a - B to a new variable c.
• Assign ['He wore a ',costume,'costume, and a ',Mask,' mask.'] to the variable sentence.
• Assign total_number_of_people^2 to the variable total_number_of_square_people.
• Try assigning a*B to the variable a times b.
• Try assigning a - B to the variable a-B.
• What limitations have you discovered in variable names?