inv.seq {sfsmisc}R Documentation

Inverse seq() - Short Expression for Index Vector

Description

Compute a short expression for a given integer vector, typically an index, that can be expressed shortly, using : etc.

Usage

inv.seq(i)

Arguments

i vector of (usually increasing) integers.

Value

an expression which can be eval()ed to return the original i.

Author(s)

Martin Maechler, Oct. 1995

See Also

rle for another kind of integer vector coding.

Examples

(rr <- inv.seq(i1 <- c(3:12, 20:24, 27, 30:33)))
eval(rr)
stopifnot(eval(rr) == i1)

e2 <- expression(c(20:13, 3:12, -1:-4, 27, 30:31))
(r2 <- inv.seq(i2 <- eval(e2)))
stopifnot(identical(e2,r2))

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