bit (version 1.1-14)

bitwhich: A class for vectors representing asymetric selections

Description

A bitwhich object like the result of which and as.which does represent integer subscript positions, but bitwhich objects represent some subscripts rather with negative integers, if this needs less space. The extreme cases of selecting all/none subscripts are represented by TRUE/FALSE. This needs less RAM compared to logical (and often less than as.which). Logical operations are fast if the selection is asymetric (only few or almost all selected).

Usage

bitwhich(maxindex, poslength = NULL, x = NULL)

Arguments

maxindex

the length of the vector (sum of all TRUEs and FALSEs)

poslength

Only use if x is not NULL: the sum of all TRUEs

x

Default NULL or FALSE or unique negative integers or unique positive integers or TRUE

Value

An object of class 'bitwhich' carrying two attributes

maxindex

see above

poslength

see above

Details

class 'bitwhich' represents a boolean selection in one of the following ways

• FALSE to select nothing

• TRUE to select everything

• unique positive integers to select those

• unique negative integers to exclude those

See Also

as.bitwhich, as.which, bit

Examples

# NOT RUN {
 bitwhich(12, x=c(1,3), poslength=2)
 bitwhich(12, x=-c(1,3), poslength=10)
# }