distinct: Distinct elements of a list

In jfrench/smerc: Statistical Methods for Regional Counts

Distinct elements of a list

Description

distinct takes a list of integer vectors and returns the list indices that contain unique combinations of elements. This function is NOT robust against misuse, so please use properly.

Usage

distinct(x, N = max(unlist(x)))

Arguments

x	A list of integers
N	The largest integer value across all elements of x.

Details

Assume that k is the largest integer value in x. A vector of the largest k prime numbers is obtained (call this pri). The algorithm takes the sum of the log of pri[x[[i]]] for each element of x, and determines which sums are unique. This is why the elements of x must be integer vectors. The prime aspect of the algorithm is critical, as it ensures that a none of the values are multiples of the others, ensuring uniqueness.

Note: this algorithm has only been applied to data sets where each element of x[[i]] appears only once, though it should work for repeats also.

Value

A vector with the distinct indices.

Author(s)

Joshua French

References

Algorithm based on suggestion at https://stackoverflow.com/a/29824978.

Examples

x <- list(1:3, 3:1, 1:4, 4:1, c(1, 2, 4, 6), c(6, 4, 1, 2))
x[distinct(x)]

jfrench/smerc documentation built on Oct. 27, 2024, 5:13 p.m.