SSBtools (version 1.7.5)

DummyDuplicated: 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)

Value

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

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)

Author

Øyvind Langsrud

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.

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))