ff: fforder – R documentation

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fforder

Sorting: order from ff vectors

Description

Returns order with regard to one or more ff vectors

Usage

fforder(...
, index = NULL
, use.index = NULL
, aux = NULL
, auxindex = NULL
, has.na = TRUE
, na.last = TRUE
, decreasing = FALSE
, BATCHBYTES = getOption("ffmaxbytes")
, VERBOSE = FALSE
)

Arguments

`...`	one of more ff vectors which define the order
`index`	an optional ff integer vector used to store the order output
`use.index`	A boolean flag telling fforder whether to use the positions in 'index' as input. If you do this, it is your responsibility to assure legal positions - otherwise you risk a crash.
`aux`	An optional named list of ff vectors that can be used for temporary copying – the names of the list identify the `vmodes` for which the respective ff vector is suitable.
`auxindex`	An optional ff intger vector for temporary storage of integer positions.
`has.na`	boolean scalar telling fforder whether the vector might contain `NA`s. Note that you risk a crash if there are unexpected `NA`s with `has.na=FALSE`
`na.last`	boolean scalar telling fforder whether to order `NA`s last or first. Note that 'boolean' means that there is no third option `NA` as in `order`
`decreasing`	boolean scalar telling fforder whether to order increasing or decreasing
`BATCHBYTES`	maximum number of RAM bytes fforder should try not to exceed
`VERBOSE`	cat some info about the ordering

Details

fforder tries to order the vector in-RAM, if not possible it uses (a yet simple) out-of-memory algorithm. Like ramorder the in-RAM ordering method is choosen depending on context information.

Value

An ff vector with the positions that ore required to sort the input as specified – with an attribute na.count with as many values as columns in ...

Author(s)

Jens Oehlschlägel

Examples

x <- ff(sample(1e5, 1e6, TRUE))
   y <- ff(sample(1e5, 1e6, TRUE))
   d <- ffdf(x, y)

   i <- fforder(y)
   y[i]
   i <- fforder(x, index=i)
   x[i]
   d[i,]

   i <- fforder(x, y)
   d[i,]

   i <- ffdforder(d)
   d[i,]

   rm(x, y, d, i)
   gc()

ff

Memory-Efficient Storage of Large Data on Disk and Fast Access Functions

v4.0.4

GPL-2 | GPL-3 | file LICENSE

Authors

Daniel Adler [aut], Christian Gläser [aut], Oleg Nenadic [aut], Jens Oehlschlägel [aut, cre], Martijn Schuemie [aut], Walter Zucchini [aut]

Initial release

2020-10-13