Package 'BiocIO'

BiocFile class objects

Description

BiocFile is the base virtual class for high-level file abstractions where subclasses are associated with a particular file format or type. It wraps a low-level representation of a file, currently either a path, URL, or connection object. We can represent a list of BiocFile objects with a BiocFileList.

Usage

BiocFileList(files)

resource(x)

resource(x) <- value

## S4 method for signature 'BiocFile'
resource(x)

## S4 replacement method for signature 'BiocFile,character_OR_connection'
resource(x) <- value

fileFormat(x)

## S4 method for signature 'character'
fileFormat(x)

## S4 method for signature 'BiocFile'
fileFormat(x)

## S4 method for signature 'BiocFile'
path(object, ...)

## S4 method for signature 'BiocFile'
show(object)

FileForFormat(path, format = file_ext(path), prefix = NULL, suffix = "File")

## S4 method for signature 'BiocFile'
as.character(x)

Arguments

files	character() A vector of file paths for the BiocFileList constructor
x	A BiocFile instance
object	A BiocFile instance
...	additional arguments to lower-level functions, not used.
path, value	Either a character or connection object to replace the original resource
format	character(1) The file extension conducive to a file class name, e.g., CSVFile
prefix	character(1) The prefix to prepend to the format class name, e.g., Spatial for a class SpatialCSV.
suffix	character(1) The suffix to append to the format class name, e.g., File for a class CSVFile.

Value

For constructors, an instance of that class. For extractors such as resource and path, typically a character vector of the file path. For FileForFormat, a convenient instance of the class for which the input file corresponds to.

Accessor Methods

In the code snippets below, x represents a BiocFile object.

• path(x): Gets the path, as a character vector, to the resource represented by the BiocFile object, if possible.

• resource(x): Gets the low-level resource, either a character vector (a path or URL) or a connection.

• fileFormat(x): Gets a string identifying the file format. Can also be called directly on a character file path, in which case it uses a heuristic based on the file extension.

FileForFormat

The prefix and suffix arguments are used to filter the class names to those that match the pattern paste0(prefix, format, suffix). If either prefix or suffix are NULL, they are ignored. Note that the search is case insensitive and does require the format to be in the name of the class.

Author(s)

Michael Lawrence

See Also

Implementing classes include: BigWigFile, TwoBitFile, BEDFile, GFFFile, WIGFile

Examples

## For our examples, we create a class called CSVFILE that extends BiocFile
.CSVFile <- setClass("CSVFile", contains = "BiocFile")

## Constructor
CSVFile <- function(resource) {
    .CSVFile(resource = resource)
}

setMethod("import", "CSVFile", function(con, format, text, ...) {
    read.csv(resource(con), ...)
})

## Define export
setMethod("export", c("data.frame", "CSVFile"),
    function(object, con, format, ...) {
        write.csv(object, resource(con), ...)
    }
)

## Recommend CSVFile class for .csv files
temp <- tempfile(fileext = ".csv")
FileForFormat(temp)

## Create CSVFile
csv <- CSVFile(temp)

## Display path of file
path(csv)

## Display resource of file
resource(csv)

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File compression

Description

Methods and generics for file compression strategies.

Usage

decompress(manager, con, ...)

## S4 method for signature 'ANY'
decompress(manager, con, ...)

## S4 method for signature 'CompressedFile'
decompress(manager, con, ...)

## S4 method for signature 'character'
decompress(manager, con, ...)

## S4 method for signature 'CompressedFile'
fileFormat(x)

Arguments

manager	The connection manager, defaults to the internal manager class
con	The connection from which data is loaded or to which data is saved. If this is a character vector, it is assumed to be a file name and a corresponding file connection is created and then closed after exporting the object. If it is a BiocFile derivative, the data is loaded from or saved to the underlying resource. If missing, the function will return the output as a character vector, rather than writing to a connection.
...	Parameters to pass to the format-specific method.
x	A BiocFile instance

Value

A decompressed representation of a CompressedFile or character object

Related functions

• FileForFormat(path, format = file_ext(path)): Determines the file type of path and returns a high-level file object such as BamFile, BEDFile, BigWigFile, etc.

Examples

file <- tempfile(fileext = ".gzip")
decompress(con = file)

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Import and export

Description

The functions import and export load and save objects from and to particular file formats.

Usage

import(con, format, text, ...)

## S4 method for signature 'connection,character,ANY'
import(con, format, text, ...)

## S4 method for signature 'connection,missing,ANY'
import(con, format, text, ...)

## S4 method for signature 'character,missing,ANY'
import(con, format, text, ...)

## S4 method for signature 'character,character,ANY'
import(con, format, text, ...)

## S4 method for signature 'missing,ANY,character'
import(con, format, text, ...)

export(object, con, format, ...)

## S4 method for signature 'ANY,connection,character'
export(object, con, format, ...)

## S4 method for signature 'ANY,connection,missing'
export(object, con, format, ...)

## S4 method for signature 'ANY,missing,character'
export(object, con, format, ...)

## S4 method for signature 'ANY,character,missing'
export(object, con, format, ...)

## S4 method for signature 'ANY,character,character'
export(object, con, format, ...)

## S4 method for signature 'CompressedFile,missing,ANY'
import(con, format, text, ...)

## S4 method for signature 'ANY,CompressedFile,missing'
export(object, con, format, ...)

Arguments

con	The connection from which data is loaded or to which data is saved. If this is a character vector, it is assumed to be a file name and a corresponding file connection is created and then closed after exporting the object. If it is a BiocFile derivative, the data is loaded from or saved to the underlying resource. If missing, the function will return the output as a character vector, rather than writing to a connection.
format	The format of the output. If missing and con is a file name, the format is derived from the file extension. This argument is unnecessary when con is a derivative of BiocFile.
text	If con is missing, this can be a character vector directly providing the string data to import.
...	Parameters to pass to the format-specific method.
object	The object to export.

Value

If con is missing, a character vector containing the string output. Otherwise, nothing is returned.

Author(s)

Michael Lawrence

See Also

Format-specific options for the popular formats: GFF, BED, Bed15, bedGraph, WIG, BigWig

Examples

## To illustrate export(), import(), and yeild(), we create a class, CSVFILE
.CSVFile <- setClass("CSVFile", contains = "BiocFile")

## Constructor
CSVFile <- function(resource) {
    .CSVFile(resource = resource)
}

## Define import
setMethod("import", "CSVFile",
    function(con, format, text, ...) {
        read.csv(resource(con), ...)
    }
)

## Define export
setMethod("export", c("data.frame", "CSVFile"),
    function(object, con, format, ...) {
        write.csv(object, resource(con), ...)
    }
)

## Usage
temp <- tempfile(fileext = ".csv")
csv <- CSVFile(temp)

export(mtcars, csv)
df <- import(csv)

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