seq {base}

R Documentation

Sequence Generation

Description

Generate regular sequences. seq is a standard generic with a default method. seq.int is an internal generic which can be much faster but has a few restrictions. seq_along and seq_len are very fast primitives for two common cases.

Usage

seq(...)

## Default S3 method:
seq(from = 1, to = 1, by = ((to - from)/(length.out - 1)),
    length.out = NULL, along.with = NULL, ...)

seq.int(from, to, by, length.out, along.with, ...)

seq_along(along.with)
seq_len(length.out)

Arguments

...	arguments passed to or from methods.
from, to	the starting and (maximal) end value of the sequence.
by	number: increment of the sequence.
length.out	desired length of the sequence. A non-negative number, which for seq and seq.int will be rounded up if fractional.
along.with	take the length from the length of this argument.

Details

The interpretation of the unnamed arguments of seq and seq.int is not standard, and it is recommended always to name the arguments when programming.

Both seq are seq.int are generic, and only the default method is described here. Typical usages are

seq(from, to)
seq(from, to, by= )
seq(from, to, length.out= )
seq(along.with= )
seq(from)
seq(length.out= )

The first form generates the sequence from, from+/-1, ..., to (identical to from:to).

The second form generates from, from+by, ..., up to the sequence value less than or equal to to. Specifying to - from and by of opposite signs is an error. Note that the computed final value can go just beyond to to allow for rounding error, but (as from R 2.9.0) is truncated to to.

The third generates a sequence of length.out equally spaced values from from to to. (length.out is usually abbreviated to length or len, and seq_len is much faster.)

The fourth form generates the sequence 1, 2, ..., length(along.with). (along.with is usually abbreviated to along, and seq_along is much faster.)

The fifth form generates the sequence 1, 2, ..., length(from) (as if argument along.with had been specified), unless the argument is numeric of length 1 when it is interpreted as 1:from (even for seq(0) for compatibility with S).

The final form generates 1, 2, ..., length.out unless length.out = 0, when it generates integer(0).

Very small sequences (with from - to of the order of 10^{-14} times the larger of the ends) will return from.

For seq(only), up to two of from, to and by can be supplied as complex values provided length.out or along.with is specified.

Value

Currently, the default method returns a result of type "integer" if from is (numerically equal to an) integer and, e.g., only to is specified, or also if only length or only along.with is specified. Note: this may change in the future and programmers should not rely on it.

References

Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.

See Also

The methods seq.Date and seq.POSIXt.

:, rep, sequence, row, col.

Examples

seq(0, 1, length.out=11)
seq(stats::rnorm(20))
seq(1, 9, by = 2) # match
seq(1, 9, by = pi)# stay below
seq(1, 6, by = 3)
seq(1.575, 5.125, by=0.05)
seq(17) # same as 1:17

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