base (version 3.3)

readRDS: Serialization Interface for Single Objects

Description

Functions to write a single Robject to a file, and to restore it.

Usage

saveRDS(object, file = "", ascii = FALSE, version = NULL,
        compress = TRUE, refhook = NULL)
readRDS(file, refhook = NULL)

Arguments

object

R object to serialize.

file

a connection or the name of the file where the R object is saved to or read from.

ascii

a logical. If TRUE or NA, an ASCII representation is written; otherwise (default), a binary one is used. See the comments in the help for save.

version

the workspace format version to use. NULL specifies the current default version (2). Versions prior to 2 are not supported, so this will only be relevant when there are later versions.

compress

a logical specifying whether saving to a named file is to use "gzip" compression, or one of "gzip", "bzip2" or "xz" to indicate the type of compression to be used. Ignored if file is a connection.

refhook

a hook function for handling reference objects.

Value

• For readRDS, an Robject.

  For saveRDS, NULL invisibly.

Details

These functions provide the means to save a single Robject to a connection (typically a file) and to restore the object, quite possibly under a different name. This differs from save and load, which save and restore one or more named objects into an environment. They are widely used by Ritself, for example to store metadata for a package and to store the help.search databases: the ".rds" file extension is most often used.

Functions serialize and unserialize provide a slightly lower-level interface to serialization: objects serialized to a connection by serialize can be read back by readRDS and conversely.

All of these interfaces use the same serialization format, which has been used since R1.4.0 (but extended from time to time as new object types have been added to R). However, save writes a single line header (typically "RDXs ") before the serialization of a single object (a pairlist of all the objects to be saved).

Compression is handled by the connection opened when file is a file name, so is only possible when file is a connection if handled by the connection. So e.g.url connections will need to be wrapped in a call to gzcon.

If a connection is supplied it will be opened (in binary mode) for the duration of the function if not already open: if it is already open it must be in binary mode for saveRDS(ascii = FALSE) or to read non-ASCII saves.

See Also

serialize, save and load.

The R Internals manual for details of the format used.

Examples

## save a single object to file
saveRDS(women, "women.rds")
## restore it under a different name
women2 <- readRDS("women.rds")
identical(women, women2)
## or examine the object via a connection, which will be opened as needed.
con <- gzfile("women.rds")
readRDS(con)
close(con)

## Less convenient ways to restore the object
## which demonstrate compatibility with unserialize()
con <- gzfile("women.rds", "rb")
identical(unserialize(con), women)
close(con)
con <- gzfile("women.rds", "rb")
wm <- readBin(con, "raw", n = 1e4) # size is a guess
close(con)
identical(unserialize(wm), women)

## Format compatibility with serialize():
con <- file("women2", "w")
serialize(women, con) # ASCII, uncompressed
close(con)
identical(women, readRDS("women2"))
con <- bzfile("women3", "w")
serialize(women, con) # binary, bzip2-compressed
close(con)
identical(women, readRDS("women2"))

<testonly>unlink(c("women.rds", "women2", "women3"))</testonly>