bit: bitwhich – R documentation

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bitwhich

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 asymetric (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` explicitely, 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

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

Classes and Methods for Fast Memory-Efficient Boolean Selections

v4.0.4

GPL-2 | GPL-3

Authors

Jens Oehlschlägel [aut, cre], Brian Ripley [ctb]

Initial release

2020-08-03