R: Replicate Elements of Vectors and Lists

rep {base} | R Documentation

## Replicate Elements of Vectors and Lists

### Description

`rep` replicates the values in `x`. It is a generic function, and the default method is described here.

`rep.int` is a faster simplified version for the commonest case.

### Usage

    rep(x, times, ...)

    ## Default S3 method:
    rep(x, times, length.out, each, ...)

    rep.int(x, times)

### Arguments

`x` | a vector (of any mode including a list) or a pairlist or a `POSIXct` or `POSIXlt` or `date` object.
`times` | optional non-negative integer. A vector giving the number of times to repeat each element if of length `length(x)`, or to repeat the whole vector if of length 1.
`length.out` | optional integer. The desired length of the output vector.
`each` | optional integer. Each element of `x` is repeated `each` times.
`...` | further arguments to be passed to or from other methods.

### Details

A least one of `times`, `length.out` and `each` must be specified, and normally exactly one is. If `length.out` is given, `times` is ignored. If `each` is specified with either of the other two, its replication is performed first, and then that implied by `times` or `length.out`.

If `times` consists of a single integer, the result consists of the values in `x` repeated this many times. If `times` is a vector of the same length as `x`, the result consists of `x[1]` repeated `times[1]` times, `x[2]` repeated `times[2]` times and so on.

`length.out` may be given in place of `times`, in which case `x` is repeated as many times as is necessary to create a vector of this length.

Non-integer values of `times` will be truncated towards zero. If `times` is a computed quantity it is prudent to add a small fuzz.

If `x` has length zero and `length.out` is supplied and is positive, the values are filled in using the extraction rules, that is by an `NA` of the appropriate class for an atomic vector and `NULL` for a list.

### Value

A vector of the same class as `x`.

### Note

If the original vector has names, these are also replicated and so will almost always contain duplicates. (In contrast, S strips the names.)

Function `rep.int` is a simple case handled by internal code, and provided as a separate function purely for S compatibility.

### References

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

### See Also

`seq`, `sequence`.

### Examples

    rep(1:4, 2)
    rep(1:4, each = 2)       # not the same.
    rep(1:4, c(2,2,2,2))     # same as second.
    rep(1:4, c(2,1,2,1))
    rep(1:4, each = 2, len = 4)    # first 4 only.
    rep(1:4, each = 2, len = 10)   # 8 integers plus two recycled 1's.
    rep(1:4, each = 2, times = 3)  # length 24, 3 complete replications

    rep(1, 40*(1-.8)) # length 7 on most platforms
    rep(1, 40*(1-.8)+1e-7) # better

    ## replicate a list
    fred <- list(happy = 1:10, name = "squash")
    rep(fred, 5)

    # date-time objects
    x <- .leap.seconds[1:3]
    rep(x, 2)
    rep(as.POSIXlt(x), rep(2, 3))

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