| seq | R Documentation |
Generate regular sequences.seq is a standard generic with adefault method.seq.int is a primitive which can bemuch faster but has a few restrictions.seq_along andseq_len are very fast primitives for two common cases.
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 passed to or from methods. |
from, to | the starting and (maximal) end values of thesequence. Of length |
by | number: increment of the sequence. |
length.out | desired length of the sequence. Anon-negative number, which for |
along.with | take the length from the length of this argument. |
Numerical inputs should all be finite (that is, not infinite,NaN orNA).
The interpretation of the unnamed arguments ofseq andseq.int isnot standard, and it is recommended always toname the arguments when programming.
seq is generic, and only the default method is described here.Note that it dispatches on the class of thefirst argumentirrespective of argument names. This can have unintended consequencesif it is called with just one argument intending this to be taken asalong.with: it is much better to useseq_along in thatcase.
seq.int is an internal generic which dispatches onmethods for"seq" based on the class of the first suppliedargument (before argument matching).
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 sequencefrom, from+/-1, ..., to(identical tofrom:to).
The second form generatesfrom, from+by, ..., up to thesequence value less than or equal toto. Specifyingto - from andby of opposite signs is an error. Note that thecomputed final value can go just beyondto to allow forrounding error, but is truncated toto. (‘Just beyond’is by up to1e-10 timesabs(from - to).)
The third generates a sequence oflength.out equally spacedvalues fromfrom toto. (length.out is usuallyabbreviated tolength orlen, andseq_len is muchfaster.)
The fourth form generates the integer sequence1, 2, ..., length(along.with). (along.with is usually abbreviated toalong, andseq_along is much faster.)
The fifth form generates the sequence1, 2, ..., length(from)(as if argumentalong.with had been specified),unlessthe argument is numeric of length 1 when it is interpreted as1:from (even forseq(0) for compatibility with S).Using eitherseq_along orseq_len is much preferred(unless strict S compatibility is essential).
The final form generates the integer sequence1, 2, ..., length.out unlesslength.out = 0, when it generatesinteger(0).
Very small sequences (withfrom - to of the order of10^{-14}times the larger of the ends) will returnfrom.
Forseq (only), up to two offrom,to andby can be supplied as complex values providedlength.outoralong.with is specified. More generally, the default methodofseq will handle classed objects with methods fortheMath,Ops andSummary group generics.
seq.int,seq_along andseq_len areprimitive.
seq.int and the default method ofseq for numericarguments return a vector of type"integer" or"double":programmers should not rely on which.
seq_along andseq_len return an integer vector, unlessit is along vector when it will be double.
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988)The New S Language.Wadsworth & Brooks/Cole.
The methodsseq.Date andseq.POSIXt.
:,rep,sequence,row,col.
seq(0, 1, length.out = 11)seq(stats::rnorm(20)) # effectively 'along'seq(1, 9, by = 2) # matches 'end'seq(1, 9, by = pi) # stays below 'end'seq(1, 6, by = 3)seq(1.575, 5.125, by = 0.05)seq(17) # same as 1:17, or even better seq_len(17)
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