R: Colon Operator

Colon {base} | R Documentation

## Colon Operator

### Description

Generate regular sequences.

### Usage

    from:to
       a:b

### Arguments

`from` | starting value of sequence.
`to` | (maximal) end value of the sequence.
`a, b` | `factor`s of the same length.

### Details

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.

### Value

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).

### References

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`.

### Examples

    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

[Package base version 2.15.1 Index]