bitmapped vectors of booleans (no NAs), coercion from and to logicals, integers and integer subscripts; fast boolean operators and fast summary statistics. With 'bit' vectors you can store true binary booleans {FALSE,TRUE} at the expense of 1 bit only, on a 32 bit architecture this means factor 32 less RAM and ~ factor 32 more speed on boolean operations. Due to overhead of R calls, actual speed gain depends on the size of the vector: expect gains for vectors of size > 10000 elements. Even for onetime boolean operations it can payoff to convert to bit, the payoff is obvious, when such components are used more than once. Reading from and writing to bit is approximately as fast as accessing standard logicals  mostly due to R's time for memory allocation. The package allows to work with preallocated memory for return values by calling .Call() directly: when evaluating the speed of Caccess with preallocated vector memory, coping from bit to logical requires only 70% of the time for copying from logical to logical; and copying from logical to bit comes at a performance penalty of 150%. the package now contains further classes for representing logical selections: 'bitwhich' for very skewed selections and 'ri' for selecting ranges of values for chunked processing. All three index classes can be used for subsetting 'ff' objects (ff2.10 and higher).
Package details 


Author  Jens Oehlschlgel <Jens.Oehlschlaegel@truecluster.com> 
Date of publication  20140409 09:54:10 
Maintainer  Jens Oehlschlgel <Jens.Oehlschlaegel@truecluster.com> 
License  GPL2 
Version  1.112 
URL  http://ff.rforge.rproject.org/ 
Package repository  View on CRAN 
Installation 
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