Inverse of a permutation
Calculates the inverse of a permutation in either word or cycle form
inverse(x) ## S3 method for class 'word' inverse(x) ## S3 method for class 'cycle' inverse(x) inverse_word_single(W) inverse_cyclist_single(cyc)
x |
Object of class |
W |
In function |
cyc |
In function |
The package provides methods to invert objects of class word
(the R idiom is W[W] <- seq_along(W)) and also objects of class
cycle (the idiom is
lapply(cyc,function(o){c(o[1],rev(o[-1]))})).
The user should use inverse() directly, which dispatches to
either inverse.word() or inverse.cycle() as appropriate.
Sometimes, using idiom such as x^-1 or id/x gives neater
code, although these may require coercion between word form and cycle
form.
Function inverse() returns an object of the same class as its argument.
Robin K. S. Hankin
x <- rperm(10,6) inverse(x) all(is.id(x*inverse(x))) # should be TRUE inverse(as.cycle(matrix(1:8,9,8)))
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