bitwhich: Create bitwhich vector (skewed boolean)

In bit: Classes and Methods for Fast Memory-Efficient Boolean Selections

Create bitwhich vector (skewed boolean)

Description

A bitwhich object represents a boolean filter like a bit() object (NAs are not allowed) but uses a sparse representation suitable for very skewed (asymmetric) selections. Three extreme cases are represented with logical values, no length via logical(), all TRUE with TRUE and all FALSE with FALSE. All other selections are represented with positive or negative integers, whatever is shorter. This needs less RAM compared to logical() (and often less than bit() or which()). Logical operations are fast if the selection is asymmetric (only few or almost all selected).

Usage

bitwhich(
  maxindex = 0L,
  x = NULL,
  xempty = FALSE,
  poslength = NULL,
  is.unsorted = TRUE,
  has.dup = TRUE
)

Arguments

maxindex	length of the vector
x	Information about which positions are FALSE or TRUE: either logical() or TRUE or FALSE or a integer vector of positive or of negative subscripts.
xempty	what to assume about parameter x if x=integer(0), typically TRUE or FALSE.
poslength	tuning: poslength is calculated automatically, you can give poslength explicitly, in this case it must be correct and x must be sorted and not have duplicates.
is.unsorted	tuning: FALSE implies that x is already sorted and sorting is skipped
has.dup	tuning: FALSE implies that x has no duplicates

Value

an object of class 'bitwhich' carrying two attributes

• maxindex: see above

• poslength: see above

See Also

bitwhich_representation(), as.bitwhich(), bit()

Examples

bitwhich()
bitwhich(12)
bitwhich(12, x=TRUE)
bitwhich(12, x=3)
bitwhich(12, x=-3)
bitwhich(12, x=integer())
bitwhich(12, x=integer(), xempty=TRUE)

bit documentation built on April 4, 2025, 3:09 a.m.