MATRIX Course

Add a matrix with another

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As long as the two matrices have the same number of lines and columns (=dimension), you can make the sum, which is the addition of their values, coefficient by coefficient.

\[ \begin{split} \begin{pmatrix} 1 & 2 & 3 \\ 4 & 5 & 6 \end{pmatrix} + \begin{pmatrix} 0 & 1 & 2 \\ 1 & 2 & 3 \end{pmatrix} = \begin{pmatrix} 1 & 3 & 5 \\ 5 & 7 & 9 \end{pmatrix}\end{split} \]

Code in R

# matrix 3x3, with (1,2,3\\4,5,6\\7,8,9)
A <- matrix(1:9, 3, 3, byrow = TRUE)
# matrix of 1
B <- matrix(rep(1, length = 9), 3, 3, byrow = TRUE)

A+B
# 		[,1] [,2] [,3]
# [1,]    2    3    4
# [2,]    5    6    7
# [3,]    8    9   10