R Vectors

Vectors in R can be created as the following:

v <- c(1, 4, 9, 16, 25)

Generate Vectors

Generate consecutive integers using the : notation

1:10 # a vector from 1 to 10

Generate regular sequence of numbers

seq(from = 1, to = 9, by = 2) # count up by 2

Repeat an element for x times

rep(42, 5) # repeat 42 for 5 times

We can get the elements of a vector with the index operator (note that R indices start from 1)

v[1] # 1

We can also extract multiple elements at once by passing a vector of indices to the index operator

v[c(1, 3)] # 1 9

Or we can extract a range of values using the : notation.

v[2:4] # 4 9 16

Most of the R operations are vectorized so we can operate on all the elements at once:

v * 5 - 3 # 2  17  42  77 122

We can filter a vector by passing a condition to the index operator

v[v %% 2 == 0]

(Note that this works because v %% 2 == 0 returns a vector of TRUE and FALSE)