Package 'mmapcharr'

File dimensions

Description

Number of lines and columns of file (and extra 'return' characters).

Usage

dim_file(file)

Arguments

file	Path to file.

Value

The number of lines and columns of file (and extra 'return' characters).

Examples

tmpfile <- tempfile()
write(0:9, tmpfile, ncolumns = 2)
dim_file(tmpfile)

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Create an Implementation of [ For Custom Matrix-Like Types

Description

extract is a function that converts different index types such as negative integer vectors or logical vectors passed to the [ function as i (e.g. X[i]) or i and j (e.g. X[i, j]) into positive integer vectors. The converted indices are provided as the i parameter of extract_vector or i and j parameters of extract_matrix to facilitate implementing the extraction mechanism for custom matrix-like types.

Usage

Extract(extract_vector, extract_matrix)

Arguments

extract_vector	A function in the form of function(x, i) that takes a subset of x based on a single vector of indices i and returns a vector.
extract_matrix	A function in the form of function(x, i, j) that takes a subset of x based on two vectors of indices i and j and returns a matrix.

Details

The custom type must implement methods for dim for this function to work. Implementing methods for nrow and ncol is not necessary as the default method of those generics calls dim internally.

This idea initially comes from package crochet.

Value

A function in the form of function(x, i, j, ..., drop = TRUE) that is meant to be used as a method for [ for a custom type.

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Class mmapchar

Description

A reference class for storing and accessing matrix-like data stored on disk in files containing only characters (digits) separated by a character.

Usage

mmapchar(file, code)

Arguments

file	Path of the file.
code	Integer vector of size 256 to access integers instead of rawToChar(as.raw(0:255), multiple = TRUE). See mmapcharr:::CODE_012 and mmapcharr:::CODE_DIGITS.

Examples

test_file <- system.file("testdata/test-windows.txt", package = "mmapcharr")
test <- mmapchar(test_file, code = mmapcharr:::CODE_012)
test[, 1:3]
test[]
readLines(test_file)

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Methods for the mmapchar class

Description

Methods for the mmapchar class

Accessor methods for class mmapchar. You can use positive and negative indices, logical indices (that are recycled) and also a matrix of indices (but only positive ones).

Dimension and type methods for class mmapchar.

Usage

## S4 method for signature 'mmapchar'
x[i, j, ..., drop = TRUE]

## S4 method for signature 'mmapchar'
dim(x)

## S4 method for signature 'mmapchar'
length(x)

Arguments

x	A mmapchar object.
i	A vector of indices (or nothing). You can use positive and negative indices, logical indices (that are recycled) and also a matrix of indices (but only positive ones).
j	A vector of indices (or nothing). You can use positive and negative indices, logical indices (that are recycled).
...	Not used. Just to make nargs works.
drop	Whether to delete the dimensions of a matrix which have one dimension equals to 1.

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mmapcharr.

Description

mmapcharr.

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Size of line

Description

Number of elements of each line of a file.

Usage

nelem(file)

Arguments

file	Path to file.

Value

The number of elements of each line of a file.

Examples

tmpfile <- tempfile()
write(1:10, tmpfile, ncolumns = 2)
nline(tmpfile)

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Number of lines

Description

Number of lines of a file.

Usage

nline(file)

Arguments

file	Path to file.

Value

The number of lines of the file.

Examples

tmpfile <- tempfile()
write(1:5, tmpfile, ncolumns = 1)
nline(tmpfile)

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