Colon Operator

Generate regular sequences.

from:to a:b
starting value of sequence.
(maximal) end value of the sequence.
a, b
factors of the same length.

The binary operator : has two meanings: for factors a:b is equivalent to interaction(a, b) (but the levels are ordered and labelled differently).

For other arguments from:to is equivalent to seq(from, to), and generates a sequence from from to to in steps of 1 or -1. Value to will be included if it differs from from by an integer up to a numeric fuzz of about 1e-7. Non-numeric arguments are coerced internally (hence without dispatching methods) to numeric---complex values will have their imaginary parts discarded with a warning.


For numeric arguments, a numeric vector. This will be of type integer if from is integer-valued and the result is representable in the R integer type, otherwise of type "double" (aka mode "numeric").For factors, an unordered factor with levels labelled as la:lb and ordered lexicographically (that is, lb varies fastest).


Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole. (for numeric arguments: S does not have : for factors.)

See Also

seq (a generalization of from:to).

As an alternative to using : for factors, interaction.

For : used in the formal representation of an interaction, see formula.

  • :
  • colon
library(base) 1:4 pi:6 # real 6:pi # integer f1 <- gl(2, 3); f1 f2 <- gl(3, 2); f2 f1:f2 # a factor, the "cross" f1 x f2
Documentation reproduced from package base, version 3.1.3, License: Part of R 3.1.3

Community examples at Jan 19, 2017 base v3.3.2

`a:b` is a conveniently easy to type alternative to [`, b)`]( ```{r} -3:6, 6) ``` You can also have `b` less than `a` ```{r} 6:-3 ``` Sequences don't have to start at a whole number. ```{r} -2.63:6.37 ``` If `b - a` isn't a whole number, then the last fraction is ignored. ```{r} (e_to_the_e <- exp(exp(1))) 0:e_to_the_e ``` If `a` is a whole number, then the result has class `integer` (even if `a` has class `numeric`). ```{r} class(3) class(-3:6) ``` Be careful, `1:n` is tricksy when `n = 0` – this is a common source of bugs. Use [`seq_len()`]( instead for this case. ```{r} n <- 3 1:3 n <- 0 1:n seq_len(n) ```