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 $0$.

Example.Quanty

M = {{11,12,13,14,15,16,17},
     {21,22,23,24,25,26,27},
     {31,32,33,34,35,36,37},
     {41,42,43,44,45,46,47},
     {51,52,53,54,55,56,57}}
 
print("")
print("Matrix.Sub(M,3)")
print(Matrix.Sub(M,3))
 
print("")
print("Matrix.Sub(M,2,4)")
print(Matrix.Sub(M,2,4))
 
print("")
print("Matrix.Sub(M,1,2,3,4)")
print(Matrix.Sub(M,1,2,3,4))

Matrix.Sub(M,3)
{ { 11 , 12 , 13 } , 
  { 21 , 22 , 23 } , 
  { 31 , 32 , 33 } }
 
Matrix.Sub(M,2,4)
{ { 11 , 12 , 13 , 14 } , 
  { 21 , 22 , 23 , 24 } }
 
Matrix.Sub(M,1,2,3,4)
{ { 13 , 14 , 15 , 16 } , 
  { 23 , 24 , 25 , 26 } }