save.ffdf: Save ffdf data.frames in a directory

In ffbase: Basic Statistical Functions for Package 'ff'

Description

save.ffdf saves all ffdf data.frames in the given dir. Each column is stored as with filename <ffdfname>$<colname>.ff. All variables given in "..." are stored in ".RData" in the same directory. The data can be reloaded by starting a R session in the directory or by using load.ffdf. Note that calling save.ffdf multiple times for the same directory will only store the ffdf's that were given in the last call.

Usage

save.ffdf(
  ...,
  dir = "./ffdb",
  clone = FALSE,
  relativepath = TRUE,
  overwrite = FALSE
)

Arguments

...	ffdf data.frames, ff vectors, or other variables to be saved in the directory
dir	path where .RData file will be saved and all columns of supplied ffdf's. It will be created if it doesn't exist.
clone	should the ff vectors be clone'd, creating a snapshot of the supplied ffdf or ff objects? This should only be necessary if you still need the ff vectors in their current storage location.
relativepath	logical if TRUE the stored ff vectors will have relative paths, making moving the data to another storage a simple copy operation.
overwrite	logical If TRUE save.ffdf will overwrite an previous stored ffdf, .Rdata file.

Details

Using save.ffdf automagically sets the finalizers of the ff vectors to "close". This means that the data will be preserved on disk when the object is removed or the R sessions is closed. Data can be deleted either using delete or by removing the directory where the object were saved (dir).

Note

When saving in the temporary directory pointed at by getOption("fftempdir"), ff assumes that the resulting files are to be deleted. Be sure to change the finalizers of the ff vectors when saving in the temporary directory.

See Also

load.ffdf

Examples

iris.ffdf <- as.ffdf(iris)

td <- tempfile()

# save the ffdf into the supplied directory
save.ffdf(iris.ffdf, dir=td)

# what in the directory?
dir(td)

#remove the ffdf from memory
rm("iris.ffdf")

# and reload the stored ffdf
load.ffdf(dir=td)

tf <- paste(tempfile(), ".zip", sep="")
packed <- pack.ffdf(file=tf, iris.ffdf)

#remove the ffdf from memory
rm("iris.ffdf")

# restore the ffdf from the packed ffdf
unpack.ffdf(tf)

ffbase documentation built on Feb. 27, 2021, 5:06 p.m.