R Language Importing .csv files


Example

Importing using base R

Comma separated value files (CSVs) can be imported using read.csv, which wraps read.table, but uses sep = "," to set the delimiter to a comma.

# get the file path of a CSV included in R's utils package
csv_path <- system.file("misc", "exDIF.csv", package = "utils")

# path will vary based on installation location
csv_path
## [1] "/Library/Frameworks/R.framework/Resources/library/utils/misc/exDIF.csv"

df <- read.csv(csv_path)

df
##    Var1 Var2
## 1  2.70    A
## 2  3.14    B
## 3 10.00    A
## 4 -7.00    A

A user friendly option, file.choose, allows to browse through the directories:

df <- read.csv(file.choose())

Notes

  • Unlike read.table, read.csv defaults to header = TRUE, and uses the first row as column names.
  • All these functions will convert strings to factor class by default unless either as.is = TRUE or stringsAsFactors = FALSE.
  • The read.csv2 variant defaults to sep = ";" and dec = "," for use on data from countries where the comma is used as a decimal point and the semicolon as a field separator.

Importing using packages

The readr package's read_csv function offers much faster performance, a progress bar for large files, and more popular default options than standard read.csv, including stringsAsFactors = FALSE.

library(readr)

df <- read_csv(csv_path)

df
## # A tibble: 4 x 2
##    Var1  Var2
##   <dbl> <chr>
## 1  2.70     A
## 2  3.14     B
## 3 10.00     A
## 4 -7.00     A