ff (version 2.2-14.2)

readwrite.ff: Reading and writing vectors (low-level)

Description

Simpe low-level interface for reading and writing vectors from ff files.

Usage

read.ff(x, i, n)
write.ff(x, i, value, add = FALSE)
readwrite.ff(x, i, value, add = FALSE)

Arguments

x

an ff object

i

a start position in the ff file

n

number of elements to read

value

vector of elements to write

add

TRUE if the values should rather increment than overwrite at the target positions

Value

read.ff returns a vector of values, write.ff returns the 'changed' ff object (like all assignment functions do) and readwrite.ff returns the values at the target position. More precisely readwrite.ff(x, i, value, add=FALSE) returns the old values at the position i while readwrite.ff(x, i, value, add=TRUE) returns the incremented values of x.

Details

readwrite.ff combines the effects of read.ff and write.ff in a single operation: it retrieves the old values starting from position i before changing them. getset.ff will maintain na.count.

See Also

getset.ff for low-level scalar access and [.ff for high-level access

Examples

# NOT RUN {
  x <- ff(0, length=12)
  read.ff(x, 3, 6)
  write.ff(x, 3, rep(1, 6))
  x
  write.ff(x, 3, rep(1, 6), add=TRUE)
  x
  readwrite.ff(x, 3, rep(1, 6), add=TRUE)
  readwrite.ff(x, 3, rep(1, 6))
  x
  rm(x); gc()
# }