6.1: Relational Operators

Suppose we have three variables, a, b, and c, and we want to check whether they form a Pythagorean triple. We can use the equality operator (==) to compare two values:

>> a = 3;
>> b = 4;
>> c = 5;
>> a^2 + b^2 == c^2

ans = logical 1

The result is a logical value, which means it’s either 1, which means “true,” or 0, which means “false.” Here’s an example where the result is false:

>> c = 6;
>> a^2 + b^2 == c^2
ans = logical 0

It’s a common error to use the assignment operator (=) instead of the equality operator (==). If you do, you get an error:

>> a^2 + b^2 = c^2
 a^2 + b^2 = c^2
           |
Error: Incorrect use of '=' operator.
To assign a value to a variable, use '='.
To compare values for equality, use '=='.

The equality operator is one of several relational operators, so called because they test relations between values. For example, x < 10 is true (1) if the value of x is less than 10 or false (0) if otherwise. And x > 0 is true if x is greater than 0.

The other relational operators are <= for “less or equal,” >= for “greater or equal,” and ~= for “not equal.”

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