Introduction to MATLAB: As seen in ENGS 20

Relational operators are important for making decisions as they allow us to compare values with each other. The following relational and equality operators share their syntax with in C, except for the negation (not) operator which is a tilde symbol ~ in MATLAB (recall that C uses an exclamation mark !):

In MATLAB, logical true is 1 and logical false is 0. Recall that in C any value other than 0 is interpreted as true. In fact, MATLAB has a logical data type, and so the result of comparing two quantities is of that datatype:

>> a = 3;
>> b = 4;
>> a == b

ans =
    logical
    0

>> a < b
ans =
    logical
    1

If two arrays are compared (must be the same size), the result is an array of logical values from an element-by-element comparison of the two arrays. This is known as a Logical Vector.

>> arr = [8  -1  2  3  9  -2  -5  -11  8  12];

>> ipos = arr >= 0
ipos =
    1×10 logical array
    1  0  1  1  1  0  0  0  1  1

>> posv = arr(ipos)
posv =
    8  2  3  9  8  12

>> wrong = [1 0 1 1 1 0 0 0 1 1]
wrong =
    1  0  1  1  1  0  0  0  1  1

>> arr(wrong)