DummyDuplicated: Duplicated columns in dummy matrix

In SSBtools: Algorithms and Tools for Tabular Statistics and Hierarchical Computations

Duplicated columns in dummy matrix

Description

The algorithm is based on crossprod(x) or crossprod(x, u) where u is a vector of random numbers

Usage

DummyDuplicated(x, idx = FALSE, rows = FALSE, rnd = FALSE)

Arguments

x	A matrix
idx	Indices returned when TRUE
rows	Duplicated rows instead when TRUE
rnd	Algorithm based on cross product with random numbers when TRUE (dummy matrix not required)

Details

The efficiency of the default algorithm depends on the sparsity of crossprod(x). The random values are generated locally within the function without affecting the random value stream in R.

Value

Logical vectors specifying duplicated columns or vector of indices (first match)

Author(s)

Øyvind Langsrud

Examples

x <- cbind(1, rbind(diag(2), diag(2)), diag(4)[, 1:2])
z <- Matrix::Matrix(x[c(1:4, 2:3), c(1, 2, 1:5, 5, 2)])

DummyDuplicated(z)
which(DummyDuplicated(z, rows = TRUE))

# Four ways to obtain the same result
DummyDuplicated(z, idx = TRUE)
DummyDuplicated(z, idx = TRUE, rnd = TRUE)
DummyDuplicated(Matrix::t(z), idx = TRUE, rows = TRUE)
DummyDuplicated(Matrix::t(z), idx = TRUE, rows = TRUE, rnd = TRUE)

# The unique values in four ways 
which(!DummyDuplicated(z), )
which(!DummyDuplicated(z, rnd = TRUE))
which(!DummyDuplicated(Matrix::t(z), rows = TRUE))
which(!DummyDuplicated(Matrix::t(z), rows = TRUE, rnd = TRUE))

SSBtools documentation built on Nov. 5, 2025, 6:51 p.m.