R: Reading and writing vectors of values (low-level)

getset.ff {ff} | R Documentation

## Reading and writing vectors of values (low-level)

### Description

The three functions `get.ff`, `set.ff` and `getset.ff` provide the simplest interface to access an ff file: getting and setting vector of values identified by positive subscripts

### Usage

    get.ff(x, i)
    set.ff(x, i, value, add = FALSE)
    getset.ff(x, i, value, add = FALSE)

### Arguments

`x` | an ff object
`i` | an index position within the ff file
`value` | the value to write to position i
`add` | TRUE if the value should rather increment than overwrite at the index position

### Details

`getset.ff` combines the effects of `get.ff` and `set.ff` in a single operation: it retrieves the old value at position `i` before changing it. `getset.ff` will maintain `na.count`.

### Value

`get.ff` returns a vector, `set.ff` returns the 'changed' ff object (like all assignment functions do) and `getset.ff` returns the value at the subscript positions. More precisely `getset.ff(x, i, value, add=FALSE)` returns the old values at the subscript positions `i` while `getset.ff(x, i, value, add=TRUE)` returns the incremented values at the subscript positions.

### Note

`get.ff`, `set.ff` and `getset.ff` are low level functions that do not support `ramclass` and `ramattribs` and thus will not give the expected result with `factor` and `POSIXct`

### Author(s)

Jens Oehlschlägel

### See Also

`readwrite.ff` for low-level access to contiguous chunks and `[.ff` for high-level access

### Examples

     x <- ff(0, length=12)
     get.ff(x, 3L)
     set.ff(x, 3L, 1)
     x
     set.ff(x, 3L, 1, add=TRUE)
     x
     getset.ff(x, 3L, 1, add=TRUE)
     getset.ff(x, 3L, 1)
     x
     rm(x); gc()

[Package ff version 2.2-13 Index]