Using the C Math Library

Overview 

Logical indexing is a special case of n-dimensional indexing. A logical index is a vector or a matrix that consists entirely of ones and zeros. Applying a logical subscript to a matrix selects the elements of the matrix that correspond to the nonzero elements in the subscript.

Logical indices are generated by the relational operator functions (mlfLt(), mlfGt(), mlfLe(), mlfGe(), mlfEq(), mlfNeq()) and by the function mlfLogical(). Because these functions attach a logical flag to a logical matrix, you cannot create a logical index simply by assigning ones and zeros to a vector or matrix.

You can form an n-dimensional logical subscript by combining a logical index with scalar, vector, matrix, or colon indices.

The examples work with matrix A and the logical array B.

A
1 4 7
2 5 8
3 6 9
B 
1 0 1
0 1 0
1 0 1

Assumptions for the Code Examples explains the conventions used in the examples.

Logical Indexing

Using a Logical Matrix as a One-Dimensional Index