Installation

The package is registered in the General registry and so can be installed at the REPL with

] add GroupedArrays.

Introduction

GroupedArray is an AbstractArray that contains positive integers or missing values.

• GroupedArray(x::AbstractArray) returns a GroupedArray of the same length as the original array, where each distinct value is encoded as a distinct integer.
• GroupedArray(xs...::AbstractArray) returns a GroupedArray where each distinct combination of values is encoded as a distinct integer
• By default (with coalesce = false), GroupedArray encodes missing values as a distinct missing category. With coalesce = true, missing values are treated similarly to other values.

Examples

using GroupedArrays
p = repeat(["a", "b", missing], outer = 2)
GroupedArray(p)
# 6-element GroupedArray{Int64, 1}:
#  1
#  2
#   missing
#  1
#  2
#   missing
p = repeat(["a", "b", missing], outer = 2)
GroupedArray(p; coalesce = true)
# 6-element GroupedArray{Int64, 1}:
#  1
#  2
#  3
#  1
#  2
#  3
p1 = repeat(["a", "b"], outer = 3)
p2 = repeat(["d", "e"], inner = 3)
GroupedArray(p1, p2)
# 6-element GroupedArray{Int64, 1}:
#  1
#  2
#  1
#  3
#  4
#  3

Relation to other packages

• GroupedArray is similar to PooledArray, except that the pool is simply the set of integers from 1 to n where n is the number of groups(missing is encoded as 0). This allows for faster lookup in setups where the group value is not meaningful.
• The algorithm to group multiple vectors is taken from DataFrames.jl