seq {base}

R Documentation

Sequence Generation

Description

Generate regular sequences.

Usage

from:to
seq(from, to)
seq(from, to, by=)
seq(from, to, length=)
seq(along)

Arguments

from	starting value of sequence.
to	(maximal) end value of the sequence.
by	increment of the sequence.
length	desired length of the sequence.
along	take the length from the length of this argument.

Details

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

The operator : and the first seq(.) form generate the sequence from, from+1, ..., to. seq is a generic function.

The second form generates from, from+by, ..., to.

The third generates a sequence of length equally spaced values from from to to.

The last generates the sequence 1, 2, ..., length(along), unless the argument is of length 1 when it is interpreted as a length argument.

If from and to are factors of the same length, then from : to returns the “cross” of the two.

Very small sequences (with from - to of the order of 1e-14 times the larger of the ends) will return from.

Value

The result is of mode "integer" if from is (numerically equal to an) integer and by is not specified.

References

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

See Also

rep, sequence, row, col.

Examples

1:4
pi:6 # float
6:pi # integer

seq(0,1, length=11)
str(seq(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

for (x in list(NULL, letters[1:6], list(1,pi)))
  cat("x=",deparse(x),";  seq(along = x):",seq(along = x),"\n")

f1 <- gl(2,3); f1
f2 <- gl(3,2); f2
f1:f2 # a factor, the ``cross''  f1 x f2

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