### RE: “matrix” is a 10 by 10 matrix defined in R, which implies it has 10 rows and 10 columns, the command matrix[ ,5] will extract ?

Suppose “matrix” is a 10 by 10 matrix defined in R, which implies it has 10 rows and 10 columns, the command matrix[ ,5] will extract

- The fifth row of the matrix as a vector.
- The fifth column of the matrix as a vector.
- The element on the fifth row and the fifth column.
- The fifth element when going through the matrix column by column from left to right.

The command matrix[,5] will extract **The fifth column of the matrix as a vector.**