Array

Arrays are also like matrices, but they allow us to have more than two dimensions. The all_prices2 row has prices of different items for January, March, and June 2018. Now, suppose we also want to record prices for 2017. We can do so by using array() and in this case we want to add two 3x3 matrices where the first one corresponds to 2018 and the latter matrix corresponds to 2017. In array(m, n, p), m and n stand for the dimensions of the matrix and p stands for how many matrices we want to store.

In the following example, we define six vectors for three different months for two different years. Now we create an array by combining six different vectors using c() and by using them inside array() as inputs as follows:

# Create six vectors
jan_2018 = c(10, 11, 20)
mar_2018 = c(20, 22, 25)
june_2018 = c(30, 33, 33)
jan_2017 = c(10, 10, 17)
mar_2017 = c(18, 23, 21)
june_2017 = c(25, 31, 35)

# Now combine these vectors into array
combined = array(c(jan_2018, mar_2018, june_2018, jan_2017, mar_2017, june_2017),dim = c(3,3,2))
combined

We can now see that we have two matrices of 3 x 3 dimensions, as in the output as follows: