Table of Contents
The quickest way to import data into R is to use the readr package. This package provides a set of functions to quickly read and write data in different formats such as CSV, TSV, and Excel. Additionally, it provides simple API’s to read and write data from databases, web services, and other sources. The readr package is designed to make it easy to import data into R and gives users the flexibility to customize the import process.
You can use the colClasses argument when importing a file into R to specify the classes of each column:
df <- read.csv('my_data.csv', colClasses=c('character', 'numeric', 'numeric'))
The benefit of using colClasses is that you can import data much faster, especially when the files are extremely large.
The following example shows how to use this argument in practice.
Example: Use colClasses When Importing Files
Suppose I have some CSV file called my_data.csv with three columns that I’d like to import into R:
I can use the following syntax to do so:
#import CSV file
df <- read.csv('my_data.csv',
colClasses=c('character', 'numeric', 'numeric'))
#view class of each column in data frame
str(df)
'data.frame': 14 obs. of 3 variables:
$ team : chr "Mavs" "Spurs" "Hornets" "Rockets" ...
$ points : num 91 99 104 103 105 88 89 93 96 99 ...
$ rebounds: num 33 23 26 25 25 26 29 30 34 23 ...
Note that the number of values in the colClasses argument should match the number of columns in the data frame.
For example, if you only supply one value to the colClasses argument then each column in the data frame will have the same class:
#import CSV file
df <- read.csv('my_data.csv',
colClasses=c('character'))
#view class of each column in data frame
str(df)
'data.frame': 14 obs. of 3 variables:
$ team : chr "Mavs" "Spurs" "Hornets" "Rockets" ...
$ points : chr "91" "99" "104" "103" ...
$ rebounds: chr "33" "23" "26" "25" ...
Notice that each column in the resulting data frame has a “character” class since we only supplied one value to the colClasses argument.
Note that you can specify the following potential classes in the colClasses argument:
- character: “hey”, “there”, “world”
- complex: as.complex(-1), 4i
- numeric: as.integer(20), 3L
- integer: 4, 12, 158
- logical: TRUE, FALSE
The following tutorials explain how to perform other common operations in R: