Using the C++ Math Library

Assigning to a Multiple Elements

Use a vector index to modify multiple elements in a matrix.

The colon() index frequently appears in the subscript of the destination because it allows you to modify an entire row or column. For example, the code

A(2,colon()) = ramp(1,3);

replaces the second row of an M-by-3 matrix with the vector 1 2 3. If we use the example matrix A, A is modified to contain:

1 4 7
1 2 3
3 6 9

You can also use a logical index to select multiple elements. For example, the assignment statement

A(A>5)= horzcat(17,17,17,17);

changes all the elements in A that are greater than 5 to 17:

1   4  17
2   5  17
3  17  17

Assigning to a Single Element

Assigning to a Subarray