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There are a few R operators and functions that are especially useful for creating vectors of non-random numbers. These functions provide multiple ways for generating sequences of numbers.
To explicitly specify numbers in a sequence you can use the colon : operator to specify all integers between two specified numbers or the combine c() function to explicity specify all numbers in the sequence.
# create a vector of integers between 1 and 10
1:10
## [1] 1 2 3 4 5 6 7 8 9 10
# create a vector consisting of 1, 5, and 10
c(1, 5, 10)
## [1] 1 5 10
# save the vector of integers between 1 and 10 as object x
x <- 1:10
x
## [1] 1 2 3 4 5 6 7 8 9 10
A generalization of : is the seq() function, which generates a sequence of numbers with a specified arithmetic progression.
# generate a sequence of numbers from 1 to 21 by increments of 2
seq(from = 1, to = 21, by = 2)
## [1] 1 3 5 7 9 11 13 15 17 19 21
# generate a sequence of numbers from 1 to 21 that has 15 equal incremented
# numbers
seq(0, 21, length.out = 15)
## [1] 0.0 1.5 3.0 4.5 6.0 7.5 9.0 10.5 12.0 13.5 15.0 16.5 18.0 19.5
## [15] 21.0
The rep() function allows us to conveniently repeat specified constants into long vectors. This function allows for collated and non-collated repetitions.
# replicates the values in x a specified number of times in a collated fashion
rep(1:4, times = 2)
## [1] 1 2 3 4 1 2 3 4
# replicates the values in x in an uncollated fashion
rep(1:4, each = 2)
## [1] 1 1 2 2 3 3 4 4