# Matrix _ Sequence -- get entry of matrix

## Synopsis

• Operator: _
• Usage:
M_(i,j)
• Inputs:
• M, , or
• i, , both integers
• Outputs:
• , the (i,j)-th entry of the matrix M, where M_(0,0) is the top left entry

## Description

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 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