Matrix _ Sequence -- get entry of matrix

Synopsis

Operator: _
Usage:

M_(i,j)
Inputs:
- M, or a mutable matrix
- i, both integers
Outputs:
- the (i,j)-th entry of the matrix M, where M_(0,0) is the top left entry, a ring element

All indexing in Macaulay2 is zero-based, so the indices start at zero.

i1 : M = matrix{{1,2,3},{0,5,6}}

o1 = | 1 2 3 |
     | 0 5 6 |

              2       3
o1 : Matrix ZZ  <-- ZZ

i2 : M_(1,2)

o2 = 6

The matrix may be a a mutable matrix too:

i3 : N = mutableMatrix M

o3 = | 1 2 3 |
     | 0 5 6 |

o3 : MutableMatrix

i4 : N_(1,0)

o4 = 0

Entries of mutable matrices can be changed:

i5 : N_(1,0) = 37

o5 = 37

i6 : N

o6 = | 1  2 3 |
     | 37 5 6 |

o6 : MutableMatrix