The Art of R Programming

General Matrix Operations

Now that we’ve covered the basics of creating a matrix, we’ll look at some common operations performed with matrices. These include performing linear algebra operations, matrix indexing, and matrix filtering.

Performing Linear Algebra Operations on Matrices

You can perform various linear algebra operations on matrices, such as matrix multiplication, matrix scalar multiplication, and matrix addition. Using y from the preceding example, here is how to perform those three operations:

> y %*% y  # mathematical matrix multiplication
  [,1] [,2]
[1,] 7   15
[2,]10   22
> 3*y  # mathematical multiplication of matrix by scalar
  [,1] [,2]
[1,] 3    9
[2,] 6   12
> y+y  # mathematical matrix addition
  [,1] [,2]
[1,] 2    6
[2,] 4    8

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