Supported file formats

rio supports a variety of different file formats for import and export. To keep the package slim, all non-essential formats are supported via “Suggests” packages, which are not installed (or loaded) by default. To ensure rio is fully functional, install these packages the first time you use rio via:

install_formats()

The full list of supported formats is below:

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.

Data Import

rio allows you to import files in almost any format using one, typically single-argument, function. import() infers the file format from the file’s extension and calls the appropriate data import function for you, returning a simple data.frame. This works for any for the formats listed above.

library("rio")

x <- import("mtcars.csv")
y <- import("mtcars.dta")

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

## [1] TRUE

If for some reason a file does not have an extension, or has a file extension that does not match its actual type, you can manually specify a file format to override the format inference step. For example, we can read in a CSV file that does not have a file extension by specifying csv:

head(import("mtcars_noext", format = "csv"))

##    mpg cyl disp  hp drat    wt  qsec vs am gear carb
## 1 21.0   6  160 110 3.90 2.620 16.46  0  1    4    4
## 2 21.0   6  160 110 3.90 2.875 17.02  0  1    4    4
## 3 22.8   4  108  93 3.85 2.320 18.61  1  1    4    1
## 4 21.4   6  258 110 3.08 3.215 19.44  1  0    3    1
## 5 18.7   8  360 175 3.15 3.440 17.02  0  0    3    2
## 6 18.1   6  225 105 2.76 3.460 20.22  1  0    3    1

str(import_list(dir()), 1)

Data Export

The export capabilities of rio are somewhat more limited than the import capabilities, given the availability of different functions in various R packages and because import functions are often written to make use of data from other applications and it never seems to be a development priority to have functions to export to the formats used by other applications. That said, rio currently supports the following formats:

library("rio")

export(mtcars, "mtcars.csv")
export(mtcars, "mtcars.dta")

It is also easy to use export() as part of an R pipeline (from magrittr or dplyr). For example, the following code uses export() to save the results of a simple data transformation:

library("magrittr")
mtcars %>%
  subset(hp > 100) %>%
  aggregate(. ~ cyl + am, data = ., FUN = mean) %>%
  export(file = "mtcars2.dta")

Some file formats (e.g., Excel workbooks, Rdata files) can support multiple data objects in a single file. export() natively supports output of multiple objects to these types of files:

# export to sheets of an Excel workbook
export(list(mtcars = mtcars, iris = iris), "multi.xlsx")

It is also possible to use the new (as of v0.6.0) function export_list() to write a list of data frames to multiple files using either a vector of file names or a file pattern:

export_list(list(mtcars = mtcars, iris = iris), "%s.tsv")

File Conversion

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.

Because convert() is just a thin wrapper for import() and export(), it is very easy to use. For example, we can convert

# create file to convert
export(mtcars, "mtcars.dta")

# convert Stata to SPSS
convert("mtcars.dta", "mtcars.sav")

convert() also accepts lists of arguments for controlling import (in_opts) and export (out_opts). This can be useful for passing additional arguments to import or export methods. This could be useful, for example, for reading in a fixed-width format file and converting it to a comma-separated values file:

# create an ambiguous file
fwf <- tempfile(fileext = ".fwf")
cat(file = fwf, "123456", "987654", sep = "\n")

# see two ways to read in the file
identical(import(fwf, widths = c(1, 2, 3)), import(fwf, widths = c(1, -2, 3)))

## Warning: The `widths` argument of `import()` is deprecated as of rio 1.0.2.
## ℹ `widths` is kept for backward compatibility. Please use `col_positions` or
##   unset `widths` to allow automatic guessing, see `?readr::read_fwf`. The
##   parameter `widths` will be dropped in v2.0.0.
## ℹ The deprecated feature was likely used in the rio package.
##   Please report the issue at <https://github.com/gesistsa/rio/issues>.
## This warning is displayed once every 8 hours.
## Call `lifecycle::last_lifecycle_warnings()` to see where this warning was
## generated.

## Rows: 2 Columns: 3
## ── Column specification ────────────────────────────────────────────────────────
## 
## dbl (3): X1, X2, X3
## 
## ℹ Use `spec()` to retrieve the full column specification for this data.
## ℹ Specify the column types or set `show_col_types = FALSE` to quiet this message.
## Rows: 2 Columns: 3
## ── Column specification ────────────────────────────────────────────────────────
## 
## dbl (3): X1, X2, X3
## 
## ℹ Use `spec()` to retrieve the full column specification for this data.
## ℹ Specify the column types or set `show_col_types = FALSE` to quiet this message.

## [1] FALSE

# convert to CSV
convert(fwf, "fwf.csv", in_opts = list(widths = c(1, 2, 3)))

## Rows: 2 Columns: 3
## ── Column specification ────────────────────────────────────────────────────────
## 
## dbl (3): X1, X2, X3
## 
## ℹ Use `spec()` to retrieve the full column specification for this data.
## ℹ Specify the column types or set `show_col_types = FALSE` to quiet this message.

import("fwf.csv") # check conversion

##   X1 X2  X3
## 1  1 23 456
## 2  9 87 654

With metadata-rich file formats (e.g., Stata, SPSS, SAS), it can also be useful to pass imported data through characterize() or factorize() when converting to an open, text-delimited format: characterize() converts a single variable or all variables in a data frame that have “labels” attributes into character vectors based on the mapping of values to value labels (e.g., export(characterize(import("file.dta")), "file.csv")). An alternative approach is exporting to CSVY format, which records metadata in a YAML-formatted header at the beginning of a CSV file.

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('mtcars.dta', 'mtcars.csv')"