Matrix
A matrix is a vector represented and accessible in two dimensions. Therefore, what applies to vectors is most likely to apply to a matrix. For example, each type of vector (for example, numeric vector or logical vectors) has its matrix version, that is, there are numeric matrices, logical matrices, and so on.
Creating a matrix
We can call matrix() to create a matrix from a vector by setting up one of its two dimensions:
matrix(c(1, 2, 3, 2, 3, 4, 3, 4, 5), ncol = 3) ## [,1] [,2] [,3] ## [1,] 1 2 3 ## [2,] 2 3 4 ## [3,] 3 4 5
By specifying ncol = 3, we mean that the provided vector should be regarded as a matrix with 3 columns (and 3 rows automatically). You may feel the original vector is not as straightforward as its representation. To make the code more user-friendly, we can write the vector in multiple lines:
matrix(c(1, 2, 3, 4, 5, 6, 7, 8, 9), nrow = 3, byrow = FALSE) ## [,1] [,2] [,3] ## [1,] 1 4 7 ## [2,] 2 5 8 ## [3,] ...
