unipos: Extract Positions of Unique Elements

Description

unipos returns the positions of those elements returned by unique.

Usage

unipos(x, incomparables = FALSE, order = c("original","values","any"), …)
# S3 method for integer64
unipos(x, incomparables = FALSE, order = c("original","values","any")
, nunique = NULL, method = NULL, …)

Arguments

a vector or a data frame or an array or NULL.

incomparables

ignored

order

The order in which positions of unique values will be returned, see details

nunique

NULL or the number of unique values (including NA). Providing nunique can speed-up when x has no cache. Note that a wrong nunique can cause undefined behaviour up to a crash.

method

NULL for automatic method selection or a suitable low-level method, see details

…

ignored

Value

an integer vector of positions

Details

This function automatically chooses from several low-level functions considering the size of x and the availability of a cache. Suitable methods are hashmapupo (simultaneously creating and using a hashmap) , hashupo (first creating a hashmap then using it) , sortorderupo (fast ordering) and orderupo (memory saving ordering).

The default order="original" collects unique values in the order of the first appearance in x like in unique, this costs extra processing. order="values" collects unique values in sorted order like in table, this costs extra processing with the hash methods but comes for free. order="any" collects unique values in undefined order, possibly faster. For hash methods this will be a quasi random order, for sort methods this will be sorted order.

Examples

Run this code

# NOT RUN {
x <- as.integer64(sample(c(rep(NA, 9), 1:9), 32, TRUE))
unipos(x)
unipos(x, order="values")

stopifnot(identical(unipos(x),  (1:length(x))[!duplicated(x)]))
stopifnot(identical(unipos(x),  match.integer64(unique(x), x)))
stopifnot(identical(unipos(x, order="values"),  match.integer64(unique(x, order="values"), x)))
stopifnot(identical(unique(x),  x[unipos(x)]))
stopifnot(identical(unique(x, order="values"),  x[unipos(x, order="values")]))
# }