Using the C++ Math Library

Using a Scalar and a Logical Vector

Let matrix X be a 4-by-4 magic square.

X = magic(4);

16   2   3  13
 5  11  10   8
 9   7   6  12
 4  14  15   1

Let B be a logical matrix that indicates which elements in row 2 of matrix X are greater than 9. B is the result of the greater than (>) operation

B = X(2, colon()) > 9;

and contains the vector

0 1 1 0

Use B as a logical index that selects those elements from matrix X.

X(2,B)

selects these elements:

11 10

Using One colon() Index and One Logical Vector as Indices

Extending Logical Indexing to N Dimensions