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How to Create Vectors in R

By Andrie de Vries, Joris Meys

To create a vector from a simple sequence of integers, for example, you use the colon operator (:) in R. The code 3:7 gives you a vector with the numbers 3 to 7, and 4:-3 creates a vector with the numbers 4 to –3, both in steps of 1.

To make bigger or smaller steps in a sequence, use the seq() function. This function’s by argument allows you to specify the amount by which the numbers should increase or decrease. For a vector with the numbers 4.5 to 2.5 in steps of 0.5, for example, you can use the following code:

> seq(from = 4.5, to = 2.5, by = -0.5)
[1] 4.5 4.0 3.5 3.0 2.5

Alternatively, you can specify the length of the sequence by using the argument length.out. R calculates the step size itself. You can make a vector of nine values going from –2.7 to 1.3 like this:

> seq(from = -2.7, to = 1.3, length.out = 9)
[1] -2.7 -2.2 -1.7 -1.2 -0.7 -0.2 0.3 0.8 1.3

You don’t have to write out the argument names if you give the values for the arguments in the correct order. The code seq(4.5, 2.5, – 0.5) does exactly the same things as seq(from = 4.5, to = 2.5, by = -0.5). If you use the argument length.out, you always have to be spell it out though.