seq {base} | R Documentation |
Generate regular sequences.
from:to a:b seq(from, to) seq(from, to, by= ) seq(from, to, length.out= ) seq(along.with= ) seq(from)
from |
starting value of sequence. |
to |
(maximal) end value of the sequence. |
by |
increment of the sequence. |
length.out |
desired length of the sequence. |
along.with |
take the length from the length of this argument. |
a,b |
factor s of same length. |
The binary operator :
has two meanings: for factors a:b
is
equivalent to interaction(a, b)
(except for labelling by
la:lb
not la.lb
). For numeric arguments a:b
is
equivalent to seq(from=a, to=b)
.
The interpretation of the unnamed arguments of seq
is
not standard, and it is recommended always to name the
arguments when programming.
Function seq
is generic, and only the default method is
described here.
The operator :
and the seq(from, to)
form generate the
sequence from, from+1, ..., to
.
The second form generates from, from+by
, ..., up to the
sequence value less than or equal to to
.
The third generates a sequence of length.out
equally spaced
values from from
to to
.
The fourth form generates the sequence 1, 2, ..., length(along.with)
.
The last generates the sequence 1, 2, ..., length(from)
(as if argument along
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).
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 10^{-14}
times the larger of the ends) will return from
.
Currently, the default method returns a result of storage
mode "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.
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.
The method seq.POSIXt
.
As an alternative to using :
for factors, interaction
.
1:4 pi:6 # float 6:pi # integer seq(0,1, length=11) 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