Описание тега matrix-indexing

Matrix indexing is a way to reference a particular element in a matrix, by specifying its row and column number.

The notion extends to multi-dimensional arrays as well.

This is a fundamental concept in many languages such as MATLAB, Octave, Python+ NumPy, R, Julia, etc...

There are several matrix-indexing methods:

• row/column indexing: M(m,n) accesses the element on the m-th row on the n-th column.
• linear indexing: this methods treats the matrix as a 1D list of elements and access the n-element. Note that there may be several ways of "flattening" the matrix row-first or column-first.
• logical indexing: by specifying a mask

The use of indexing can often improve performance in the context of code vectorization, as it can replace for-loops, if conditions, etc.