Vectors in R

Sometimes in R we just need a range of numbers. For example, we might need numbers one through ten, to iterate through sometime ten times. Or we might need numbers one through one hundred from which to take random samples. Typing out numbers one through ten doesn't take much effort:

> c(1,2,3,4,5,6,7,8,9,10)
 [1]  1  2  3  4  5  6  7  8  9 10

> ten <- c(1,2,3,4,5,6,7,8,9,10)
> ten
 [1]  1  2  3  4  5  6  7  8  9 10

Easy-peasy doing one through ten, but typing out one through one hundred isn't going to happen. Instead, we'll use a vector. It's one of the simplest data types in R, being "...a single entity consisting of an ordered collection of numbers." We create vectors using the colon (":") symbol between two numbers. Here's a vector with values from one to five:

> 1:5
[1] 1 2 3 4 5

Vectors count from the first value supplied to the last. We can make them count backwards:

> 5:1
[1] 5 4 3 2 1

Negative numbers are also possible:

> -5:5
 [1] -5 -4 -3 -2 -1  0  1  2  3  4  5

We can feed vectors into other functions. If we wanted a random sample of numbers one through one hundred, we can use a vector and the sample() function:

> sample(1:100, 1)
[1] 79

In this case we got 79, and we didn't have to type out all one hundred values to sample from manually. It's also possible to do math using vectors. Multiplication, division, and other operations are all on the table. For example, we might want to multiple all numbers between one and twenty by 0.99:

> 1:20 * 0.99
[1]  0.99  1.98  2.97  3.96  4.95  5.94  6.93  7.92  8.91  9.90 10.89 11.88 12.87 13.86 14.85 15.84 16.83 17.82 18.81 19.80

Vectors could save us a lot of time with repeat operations. However, while vectors are pretty great and easy to use, they can't do everything we might like. For example, they always increment by one. If we needed a series of numbers from zero to five in increments of 0.25, it couldn't happen with just a vector. For more fine-grained control we'll need to use the seq() function, but that's another article.