R Language Reading and writing tabular data in plain-text files (CSV, TSV, etc.) Importing with data.table
Example
The data.table package introduces the function fread. While it is similar to read.table, fread is usually faster and more flexible, guessing the file's delimiter automatically.
# 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 R installation location
csv_path
## [1] "/Library/Frameworks/R.framework/Resources/library/utils/misc/exDIF.csv"
dt <- fread(csv_path)
dt
## Var1 Var2
## 1: 2.70 A
## 2: 3.14 B
## 3: 10.00 A
## 4: -7.00 A
Where argument input is a string representing:
- the filename (e.g.
"filename.csv"), - a shell command that acts on a file (e.g.
"grep 'word' filename"), or - the input itself (e.g.
"input1, input2 \n A, B \n C, D").
fread returns an object of class data.table that inherits from class data.frame, suitable for use with the data.table's usage of []. To return an ordinary data.frame, set the data.table parameter to FALSE:
df <- fread(csv_path, data.table = FALSE)
class(df)
## [1] "data.frame"
df
## Var1 Var2
## 1 2.70 A
## 2 3.14 B
## 3 10.00 A
## 4 -7.00 A
Notes
freaddoes not have all same options asread.table. One missing argument isna.comment, which may lead in unwanted behaviors if the source file contains#.freaduses only"forquoteparameter.freaduses few (5) lines to guess variables types.
