The $3 \times 4$ matrix of ones

Example · High school

\[\begin{bmatrix} 1 & 1 & 1 & 1 \\ 1 & 1 & 1 & 1 \\ 1 & 1 & 1 & 1 \end{bmatrix}\]

Terms

Term	This example	Why
array rank	$2$	The $3 \times 4$ matrix of ones has array rank $2$, because it takes two indices (row and column) to pick out an entry.
shape	$(3, 4)$	In NumPy, a.shape is (3, 4). In MATLAB, size(A) is [3 4].
array size	$3 \cdot 4 = 12$	In NumPy, a.size is $12$. In MATLAB, numel(A) is $12$.
matrix rank	$1$	The rank of the $3 \times 4$ matrix of ones is $1$, because every row is $(1, 1, 1, 1)$. The $3 \times 4$ matrix of ones has matrix rank $1$, because all of its columns are equal, so only one is linearly independent.

All examples · All distinctions · All definitions