rio: A Swiss-Army Knife for Data I/O

The aim of rio is to make data file I/O in R as easy as possible by implementing three simple functions in Swiss-army knife style:

• export() and import() provide a painless data I/O experience by automatically choosing the appropriate data read or write function based on file extension
• convert() wraps import() and export() to allow the user to easily convert between file formats (thus providing a FOSS replacement for programs like Stat/Transfer or Sledgehammer). Luca Braglia has created a Shiny app called rioweb that provides access to the file conversion features of rio.

Supported file formats

rio supports a variety of different file formats for import and export.

Additionally, any format that is not supported by rio but that has a known R implementation will produce an informative error message pointing to a package and import or export function. Unrecognized formats will yield a simple "Unrecognized file format" error.

Examples

Because rio is meant to streamline data I/O, the package is extremely easy to use. Here are some examples of reading, writing, and converting data files.

Export

Exporting data is handled with one function, export():

library("rio")

export(mtcars, "mtcars.csv") # comma-separated values
export(mtcars, "mtcars.rds") # R serialized
export(mtcars, "mtcars.sav") # SPSS

Import

Importing data is handled with one function, import():

x <- import("mtcars.csv")
y <- import("mtcars.rds")
z <- import("mtcars.sav")

# confirm data match
all.equal(x, y, check.attributes = FALSE)

## [1] TRUE

all.equal(x, z, check.attributes = FALSE)

## [1] TRUE

Note: Because of inconsistencies across underlying packages, the data.frame returned by import might vary slightly (in variable classes and attributes) depending on file type.

Convert

The convert() function links import() and export() by constructing a dataframe from the imported file and immediately writing it back to disk. convert() invisibly returns the file name of the exported file, so that it can be used to programmatically access the new file.

convert("mtcars.sav", "mtcars.dta")

It is also possible to use rio on the command-line by calling Rscript with the -e (expression) argument. For example, to convert a file from Stata (.dta) to comma-separated values (.csv), simply do the following:

Rscript -e "rio::convert('iris.dta', 'iris.csv')"

Package Philosophy

The core advantage of rio is that it makes assumptions that the user is probably willing to make. Eight of these are important:

1. rio uses the file extension of a file name to determine what kind of file it is. This is the same logic used by Windows OS, for example, in determining what application is associated with a given file type. By taking away the need to manually match a file type (which a beginner may not recognize) to a particular import or export function, rio allows almost all common data formats to be read with the same function. Other packages do this as well, but rio aims to be more complete and more consistent than each:

• reader handles certain text formats and R binary files
• io offers a set of custom formats
• SchemaOnRead iterates through a large number of possible import methods until one works successfully

2. rio uses uses data.table::fread() for text-delimited files to automatically determine the file format regardless of the extension. So, a CSV that is actually tab-separated will still be correctly imported.

3. rio, wherever possible, does not import character strings as factors.

4. rio stores metadata from rich file formats (SPSS, Stata, etc.) in variable-level attributes in a consistent form regardless of file type or underlying import function.

5. rio supports web-based imports from SSL (HTTPS) URLs, from shortened URLs, and from URLs that lack proper extensions.

6. rio imports from from single-file .zip and .tar archives automatically, without the need to explicitly decompress them.

7. rio imports and exports files based on an internal S3 class infrastructure. This means that other packages can contain extensions to rio by importing .import() and/or .export() and then writing internal S3 methods. These methods should take the form .import.rio_X() and .export.rio_X(), where X is the file extension of a file type. An example is provided in the rio.db package.

8. rio wraps a variety of faster, more stream-lined I/O packages than those provided by base R or the foreign package. It uses haven for reading and writing SAS, Stata, and SPSS files, the fread function from data.table for delimited formats, smarter and faster fixed-width file import and export routines, and readxl for reading from Excel workbooks.

Package Installation

The package is available on CRAN and can be installed directly in R using:

install.packages("rio")

The latest development version on GitHub can be installed using devtools:

if(!require("ghit")){
    install.packages("ghit")
}
ghit::install_github("leeper/rio")