which_are_constant {dataPreparation}

Identify constant columns

Description

Find all the columns that are constant.

Usage

which_are_constant(data_set, keep_cols = NULL, verbose = TRUE)

Arguments

data_set

Matrix, data.frame or data.table

keep_cols

List of columns not to drop (list of character, default to NULL)

verbose

Should the algorithm talk (logical, default to TRUE)

Details

Algorithm is performing exponential search: it check constancy on row 1 to 10, if it's not constant it stops, if it's constant then on 11 to 100 ...
If you have a lot of columns than aren't constant, this function is way faster than a simple length(unique())! The larger the data_set set is, the more interesting it is to use this function.

Value

List of column's indexes that are constant in the data_set set.

Examples

# Let's load our data_set
data(tiny_messy_adult)

# Let's try our function
which_are_constant(tiny_messy_adult)
# Indeed it return constant the name of the constant column.