Sub

Matrix.Sub($M$,$n$) takes a Matrix $M$ and returns the upper left submatrix of size $n\times n$.

Matrix.Sub($M$,$r$,$c$) takes a Matrix $M$ and returns the upper left submatrix of size $r \times c$.

Matrix.Sub($M$, $r_0$, $r$, $c_0$, $c$) takes a Matrix $M$ and returns a submatrix of size $r \times c$, where the $1,1$ element of the new matrix coincides with the $r_0,c_0$ element of $M$. Note that in this case the first entry of a row or a column is indexed $1$, not $0$.

One of these days an example will appear here.

Example.Quanty

-- some example code

text produced as output