permute (version 0.9-8)

numPerms: Number of possible permutations for a given object

Description

numPerms calculates the maximum number of permutations possible under the current permutation scheme.

Usage

numPerms(object, control = how())

Value

The (numeric) number of possible permutations of observations in

object.

Arguments

object

any object handled by nobs.

control

a list of control values describing properties of the permutation design, as returned by a call to how.

Author

Gavin Simpson

Details

Function numPerms returns the number of permutations for the passed object and the selected permutation scheme. object can be one of a data frame, matrix, an object for which a scores method exists, or a numeric or integer vector. In the case of a numeric or integer vector, a vector of length 1 can be used and it will be expanded to a vector of length object (i.e., 1:object) before computing the number of permutations. As such, object can be the number of observations not just the object containing the observations.

See Also

shuffle and how. Additional nobs methods are provide, see nobs-methods.

Examples

## permutation design --- see ?how
ctrl <- how() ## defaults to freely exchangeable

## vector input
v <- 1:10
(obs <- nobs(v))
numPerms(v, control = ctrl)

## integer input
len <- length(v)
(obs <- nobs(len))
numPerms(len, control = ctrl)

## new design, objects are a time series
ctrl <- how(within = Within(type = "series"))
numPerms(v, control = ctrl)
## number of permutations possible drastically reduced...
## ...turn on mirroring
ctrl <- how(within = Within(type = "series", mirror = TRUE))
numPerms(v, control = ctrl)

## Try blocking --- 2 groups of 5
bl <- numPerms(v, control = how(blocks = gl(2,5)))
bl

## should be same as
pl <- numPerms(v, control = how(plots = Plots(strata = gl(2,5))))
pl
stopifnot(all.equal(bl, pl))