dim
Basics
dim is a function that allows us to return or set the dimension of an object. We read the output/input of dim as [rows, columns].
Examples
How do I get the dimensions of a dataset?
Click to see solution
# R built-in: Biochemical Oxygen Demand Dataset
BOD
# Getting dimension of the above dataset
dim(BOD)Time demand 1 1 8.3 2 2 10.3 3 3 19.0 4 4 16.0 5 5 15.6 6 7 19.8 [1] 6 2
How do I change the dimensions of an object?
Click to see solution
#Let's set x to include every number from 1 to 9.
x <- 1:9
x[1] 1 2 3 4 5 6 7 8 9
As we can see, x is a one-dimensional vector with 9 values, which we can say is 1 row and 9 columns. Let’s make x a matrix with 3 rows and 3 columns.
dim(x) <- c(3, 3)
x[,1] [,2] [,3] [1,] 1 4 7 [2,] 2 5 8 [3,] 3 6 9
As we can see from this example, R fills the columns before the rows when changing a vector to a matrix.