Saturday, December 5, 2015

What is a submatrix? Contiguous?

I always thought that a submatrix is a contiguous part of a matrix. Like

image

as shown in http://mathworld.wolfram.com/Submatrix.html.

However in https://en.wikipedia.org/wiki/Matrix_(mathematics)#Submatrix there is a different definition: take any number of rows and columns away and the result is a submatrix:

image 

This version will allow non-contiguous regions to be part of the submatrix.