# Colon

##### Colon Operator

Generate regular sequences.

- Keywords
- manip

##### 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

`library(base)`

```
# NOT RUN {
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 3.5.1, License: Part of R 3.5.1*

### Community examples

**richie@datacamp.com**at Jan 19, 2017 base v3.3.2

`a:b` is a conveniently easy to type alternative to [`seq.int(a, b)`](https://www.rdocumentation.org/packages/base/topics/seq) ```{r} -3:6 seq.int(-3, 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()`](https://www.rdocumentation.org/packages/base/topics/seq) instead for this case. ```{r} n <- 3 1:3 n <- 0 1:n seq_len(n) ```