vec_unique: Find and count unique values

Description

vec_unique(): the unique values. Equivalent to unique().
vec_unique_loc(): the locations of the unique values.
vec_unique_count(): the number of unique values.

Usage

vec_unique(x)
vec_unique_loc(x)
vec_unique_count(x)

Arguments

A vector (including a data frame).

Value

vec_unique(): a vector the same type as x containining only unique values.
vec_unique_loc(): an integer vector, giving locations of unique values.
vec_unique_count(): an integer vector of length 1, giving the number of unique values.

Missing values

In most cases, missing values are not considered to be equal, i.e. NA == NA is not TRUE. This behaviour would be unappealing here, so these functions consider all NAs to be equal. (Similarly, all NaN are also considered to be equal.)

Performance

These functions are currently slightly slower than their base equivalents. This is primarily because they do a little more checking and coercion in R, which makes them both a litter safer and more generic. Additionally, the C code underlying vctrs has not yet been implemented: we expect some performance improvements when that happens.

Examples

Run this code

# NOT RUN {
x <- rpois(100, 8)
vec_unique(x)
vec_unique_loc(x)
vec_unique_count(x)

# `vec_unique()` returns values in the order that encounters them
# use sort = "location" to match to the result of `vec_count()`
head(vec_unique(x))
head(vec_count(x, sort = "location"))

# Normally missing values are not considered to be equal
NA == NA

# But they are for the purposes of considering uniqueness
vec_unique(c(NA, NA, NA, NA, 1, 2, 1))
# }

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