Disordered indices with the `disordR` package: an introduction to class `disindex`
Robin Hankin
2023-03-22
Source:vignettes/disindex.Rmd
disindex.Rmd
Experimental S4
class disindex
allows
extraction methods, including list extraction, to operate with the
output of which()
. Consider the following R session:
## Loading required package: Matrix
## A disord object with hash 180e07f48a0c457c3ef402d4df6baf56571730bc and elements
## [1] 4 6 1 2 3 4 5 1
## (in some order)
ind <- which(d>4)
Above, object ind
points to those elements of
d
which exceed 4. Thus:
d
## A disord object with hash 180e07f48a0c457c3ef402d4df6baf56571730bc and elements
## [1] 4 6 1 2 3 4 5 1
## (in some order)
d[ind]
## A disord object with hash 600cdbc0166863107ad73437121113cd73e29f4c and elements
## [1] 6 5
## (in some order)
d[ind] <- 99
d
## A disord object with hash a9c71dbf6185fa54f934401718f7840db04853ed and elements
## [1] 4 99 1 2 3 4 99 1
## (in some order)
However, we cannot assert that ind
is elements 2 and 7
of d
, for the elements of d
are stored in an
implementation-specific order. If we examine ind
directly,
we see:
ind
## A disind object with hash 180e07f48a0c457c3ef402d4df6baf56571730bc and 2 (implementation-specific) elements
which correctly says that the elements of ind
are
implementation-specific. However, the main application of
disindex
objects is for list extraction.
## A disord object with hash af512ffc24f4ea225e72cf71ae91670255c4115d and elements
## [[1]]
## [1] 5 4
##
## [[2]]
## [1] 5 4 3 2 1
##
## [[3]]
## [1] 5 6
##
## [[4]]
## [1] 5 4 3 2
##
## (in some order)
Suppose I wish to extract from object dl
just the
element with the longest length. Noting that this would be a
disord
-compliant question, we would use:
## [1] 5 4 3 2 1