Package 'csvwr'

Retrieve the base URI from configuration

Description

Retrieve the base URI from configuration

Usage

base_uri()

Value

returns the value of csvwr_base_uri option, defaulting to example.net

Examples

## Not run: 
base_uri() # returns default

options(csvwr_base_uri="http://www.w3.org/2013/csvw/tests/")
base_uri()

## End(Not run)

---

Coalesce value to truthiness

Description

Determine whether the input is true, with missing values being interpreted as false.

Usage

coalesce_truth(x)

Arguments

x	logical, NA or NULL

Value

FALSE if x is anything but TRUE

---

Create tabular metadata from a list of tables

Description

The table annotations should each be a list with keys for url and tableSchema. You can use derive_table_schema to derive a schema from a data frame.

Usage

create_metadata(tables)

Arguments

tables

a list of csvw:table annotations

Value

a list describing a tabular metadata annotation

Examples

d <- data.frame(foo="bar")
table <- list(url="filename.csv", tableSchema=derive_table_schema(d))
create_metadata(tables=list(table))

---

Convert a csvw metadata to a list (csv2json)

Description

Convert a csvw metadata to a list (csv2json)

Usage

csvw_to_list(csvw)

Arguments

csvw	a csvw metadata list

Value

a list following the csv2json translation rules

Examples

## Not run: 
csvw_to_list(read_csvw("example.csv"))

## End(Not run)

---

Get path to csvwr example

Description

The csvwr package includes some example csvw files in it's inst/extdata directory. You can use this function to find them.

Usage

csvwr_example(path = NULL)

Arguments

path	The filename. If NULL, the example files will be listed.

Details

Inspired by readr::readr_example()

Value

either a file path or a vector of filenames

Examples

csvwr_example()
csvwr_example("computer-scientists.csv")

---

Map csvw datatypes to R types

Description

Translate csvw datatypes to R types. This implementation currently targets readr::cols column specifications.

Usage

datatype_to_type(datatypes)

Arguments

datatypes

a list of csvw datatypes

Value

a readr::cols specification - a list of collectors

Examples

## Not run: 
cspec <- datatype_to_type(list("double", list(base="date", format="yyyy-MM-dd")))
readr::read_csv(readr::readr_example("challenge.csv"), col_types=cspec)

## End(Not run)

---

CSVW default dialect

Description

The CSVW Default Dialect specification described in CSV Dialect Description Format.

Usage

default_dialect

Format

An object of class list of length 13.

Value

a list specifying a default csv dialect

---

Create a default table schema given a csv file and dialect

Description

If neither the table nor the group have a tableSchema annotation, then this default schema will used.

Usage

default_schema(filename, dialect = default_dialect)

Arguments

filename	a csv file
dialect	specification of the csv's dialect (default: default_dialect)

Value

a table schema

---

Derive csvw metadata from a csv file

Description

Derive csvw metadata from a csv file

Usage

derive_metadata(filename)

Arguments

filename

a csv file

Value

a list of csvw metadata

Examples

derive_metadata(csvwr_example("computer-scientists.csv"))

---

Derive csvw table schema from a data frame

Description

Derive csvw table schema from a data frame

Usage

derive_table_schema(d)

Arguments

d	a data frame

Value

a list describing a csvw:tableSchema

Examples

derive_table_schema(data.frame(a=1,b=2))

---

Extract a referenced table from CSVW metadata

Description

Extract a referenced table from CSVW metadata

Usage

extract_table(csvw, reference)

Arguments

csvw	the metadata
reference	a foreign key reference expressed as a list containing either a reference attribute or a schemaReference attribute

Value

a csvw table

---

Normalise metadata

Description

The spec defines a normalisation process.

Usage

normalise_metadata(metadata, location)

Arguments

metadata	a csvw metadata list
location	the location of the metadata

Value

metadata with normalised properties

---

Read CSV on the Web

Description

If the argument to filename is a json metadata document, this will be used to find csv files for each table using the value of csvw:url.

Usage

read_csvw(filename, metadata = NULL)

Arguments

filename	a path for a csv table or a json metadata document
metadata	optional user metadata

Details

If the argument to filename is a csv file, and no metadata is provided, an attempt is made to derive metadata.

If the argument to filename is a csv file, and the metadata is provided, then the given csv will override the value of csvw:url.

The csvw metadata is returned as a list. In each table in the table group, an element named dataframe is added which provides the contents of the csv table parsed into a data frame using the table schema.

Value

csvw metadata list, with a dataframe property added to each table

Examples

## Not run: 
read_csvw("metadata.json")
read_csvw("table.csv", "metadata.json")

## End(Not run)

---

Read a data frame from the first table in a csvw

Description

Wrapper around read_csvw convenient when you're only interested in the data and there's only one table

Usage

read_csvw_dataframe(filename, metadata = NULL)

Arguments

filename	a path for a csv table or a json metadata document
metadata	optional user metadata

Value

A data frame parsed using the table schema

---

Read and parse CSVW Metadata

Description

Reads in a json document as a list, transforming columns specifications into a dataframe.

Usage

read_metadata(filename)

Arguments

filename

a path for a json metadata document

Value

csvw metadata list

---

Render URI templates

Description

Interpolate variable bindings into a URI template.

Usage

render_uri_templates(templates, bindings = NULL, ...)

Arguments

templates	a character vector with URI templates
bindings	a list of variable bindings to be interpolated into templates
...	further bindings specified as named function arguments

Details

This doesn't yet implement the whole of RFC 6570, just enough to make the tests pass

You can bind variables by passing a list to the explicit bindings argument, or variadically with ... by naming arguments according to the variable name you wish to bind.

Value

a character vector with the expanded URI

Examples

render_uri_templates("{+url}/resource?query=value", list(url="http://example.net"))
render_uri_templates("{+url}", url="http://example.net")

---

Transform date/time format string from Unicode TR35 to POSIX 1003.1

Description

As per the csvw specification for date and time formats we accept format strings using the date field symbols defined in unicode TR35. These are converted to POSIX 1003.1 date format strings for use in base::strptime() or readr::parse_date()/readr::parse_datetime().

Usage

transform_datetime_format(format_string)

Arguments

format_string

a UAX35 date format string

Value

a POSIX date format string

Examples

## Not run: 
fmt <- transform_datetime_format("dd.MM.yyyy")
strptime("01.01.2001", format=fmt)

## End(Not run)

---

Map R types to csvw datatype

Description

Translate R types to csvw datatypes. Acts as an inverse of datatype_to_type but doesn't provide a 1:1 correspondence.

Usage

type_to_datatype(types)

Arguments

types

a list of R types

Value

a list of csvw datatypes

---

Validate CSVW specification

Description

Follows the csvw table validation procedure.

Usage

validate_csvw(csvw)

Arguments

csvw	a csvw metadata specification (a list)

Value

a validation report (list)

---

Validate the referential integrity of a csvw table group

Description

Fails if foreign keys aren't found in the referenced tables

Usage

validate_referential_integrity(csvw)

Arguments

csvw	the metadata annotation

Value

a list specifying any foreign key violations

---