## MATRIX Course

# Multiply a matrix by a real

This is as simple as you could guess. Simply multiply each coefficient by the real.

\[
\begin{split}-2 *
\begin{pmatrix}
1 & 2 & 3 \\
4 & 5 & 6
\end{pmatrix}
\ = \
\begin{pmatrix}
-2 & -4 & -6 \\
-8 & -10 & -12
\end{pmatrix}\end{split}
\]

## Code in R

```
# matrix 3x3, with (1,2,3\\4,5,6\\7,8,9)
A <- matrix(1:9, 3, 3, byrow = TRUE)
A * -1
# [,1] [,2] [,3]
# [1,] -1 -2 -3
# [2,] -4 -5 -6
# [3,] -7 -8 -9
```