readr

The goal of readr is to provide a fast and friendly way to read data into R. It will eventually encompass the functionality provided by read.csv(), read.table(), read.delim() and read.fwf().

Installation

Currently, readr is not available from CRAN, but you can try out the dev version with:

install_github("hadley/readr")

Usage

library(readr)
library(dplyr)

mtcars_path <- tempfile(fileext = ".csv")
write.csv(mtcars, mtcars_path, row.names = FALSE)

# Read a csv file into a data frame
read_csv(mtcars_path)
# Read lines into a vector
read_lines(mtcars_path)
# Read whole file into a single string
read_file(mtcars_path)

Output

read_csv() produces a data frame with the following properties:

• Characters are never automatically converted to factors (i.e. no more stringsAsFactors = FALSE).

• Column names are left as is, not munged into valid R identifiers.

• The data frame is given class c("tbl_df", "tbl", "data.frame") so if you also use dplyr you'll get an enhanced display.

• Row names are never set.

Compared to base functions

Compared to the corresponding base functions, readr functions:

• Return "modern" data frames, as described above.

• Use a consistent naming scheme for the parameters (e.g. col_names and col_types not header and colClasses).

• Are much faster (up to 10x faster).

Compared to fread()

data.table has a similar function called fread. Compared to fread, readr:

• Is slower. (It's currently much slower, but will always be at least 20% slower than fread.) If you want absolutely the best performance, use data.table::fread().

• readr has a slightly more sophisticated csv parser, and automatically unescape doubled quotes (e.g. "a""b" is read in as a"b).

• fread() save you work by automatically guessing the delimiter, whether or not the file has a header, how many lines to skip by default and more. Readr always forces you to supply these parameters.

• The underlying designs are quite difference. Readr is designed to be fairly general so dealing with new types of rectangular data just requires implementing a new tokenizer. fread is pure C, readr is C++ (and Rcpp).

Acknowledgements

A big set of thanks to:

• Joe Cheng for showing me the beauty of deterministic finite automata for parsing, and for teaching me why I should write a tokenizer.

• JJ Allaire for helping me come up with a design that makes very few copies.

• Dirk Eddelbuettel for coming up with the name!