R: Reading and writing vectors extended to handle logical 'ff'...

[.ff {ffbase}

R Documentation

Reading and writing vectors extended to handle logical `ff` vectors as indexes

Description

Package ff does not allow to extract and set values of ff vectors based on logical ff vectors. For this reason the extractor functions [.ff and [<-.ff defined in package ff are overloaded.
If you supply a logical ff vector as an index to another ff vector, the overloaded function will convert it to an integer ff. index before using the [.ff and [<-.ff function from the ff package.
This allows to do ff(1:10)[ff(c(FALSE, TRUE, NA, TRUE))]

Mark that all other functionality from the extractor functions [.ff and [<-.ff in package ff are retained. This is an extension to handle logical ff vectors as indexes.

Usage

## S3 method for class 'ff'
 x[i, pack = FALSE]

## S3 replacement method for class 'ff'
 x[i, add = FALSE, pack = FALSE] <- value

Arguments

`x`	an `ff` object
`i`	missing OR a single index expression OR a `hi` object
`pack`	FALSE to prevent rle-packing in hybrid index preprocessing, see `as.hi`
`add`	TRUE if the values should rather increment than overwrite at the target positions, see `readwrite.ff`
`value`	the values to be assigned, possibly recycled

Value

See Extract.ff. Mark that if a logical ff vector is used for i, and if only FALSE or NA values are present, NULL is returned in case of the extractor function [.ff while for the setter function [<-.ff, if the length value is zero, this is not allowed.

Examples

## extractors
x <- ff(1:10)
y <- ff(11:20)
idx <- ff(c(FALSE, TRUE, NA, TRUE))
x[idx]
idx <- ff(c(FALSE, FALSE, TRUE))
x[idx]
idx <- ff(1:3)
x[idx]

## setters
idx <- ff(c(FALSE, TRUE, NA, TRUE))
x[idx] <- y[idx]
x
idx <- ff(c(FALSE, FALSE, TRUE))
try(x[idx] <- y[idx], silent = T) ## not allowed
x
idx <- ff(1:3)
x[idx] <- y[idx]
x

[Package ffbase version 0.12.8 Index]