What are the most used data import functions in R
Read csv files
> tags = read.csv("C:\\Users\\Ajay Tech\\Downloads\\ml-20m\\ml-20m\\tags.csv")
Read files with any separator
tags = read.table("C:\\Users\\FGT0008\\Downloads\\ml-20m\\ml-20m\\tags.csv",
sep="\t", # tab separator
header = TRUE,
na.strings = "NA")
Read JSON files
# Read JSON file from weather.com website
> weather = fromJSON(file="http://api.openweathermap.org/data/2.5/weather?q=chicago&APPID=37a81ae1e682ac417883b0a3xxxxxx")
This result is a list
> str(weather)
List of 12
$ coord :List of 2
..$ lon: num -87.6
..$ lat: num 41.9
$ weather :List of 2
..$ :List of 4
.. ..$ id : num 701
.. ..$ main : chr "Mist"
.. ..$ description: chr "mist"
.. ..$ icon : chr "50d"
..$ :List of 4
.. ..$ id : num 721
.. ..$ main : chr "Haze"
.. ..$ description: chr "haze"
.. ..$ icon : chr "50d"
$ base : chr "stations"
$ main :List of 5
..$ temp : num 292
..$ pressure: num 1013
..$ humidity: num 100
..$ temp_min: num 290
..$ temp_max: num 294
$ visibility: num 4828
$ wind :List of 2
..$ speed: num 1.48
..$ deg : num 258
$ clouds :List of 1
..$ all: num 1
$ dt : num 1.53e+09
$ sys :List of 6
..$ type : num 1
..$ id : num 966
..$ message: num 0.0043
..$ country: chr "US"
..$ sunrise: num 1.53e+09
..$ sunset : num 1.53e+09
$ id : num 4887398
$ name : chr "Chicago"
$ cod : num 200
The JSON stream looks like this.
{"coord":{"lon":-87.62,"lat":41.88},"weather":[{"id":701,"main":"Mist","description":"mist","icon":"50d"},{"id":721,"main":"Haze","description":"haze","icon":"50d"}],"base":"stations","main":{"temp":291.91,"pressure":1013,"humidity":100,"temp_min":290.15,"temp_max":294.15},"visibility":4828,"wind":{"speed":1.48,"deg":258},"clouds":{"all":1},"dt":1530185760,"sys":{"type":1,"id":966,"message":0.0043,"country":"US","sunrise":1530181076,"sunset":1530235782},"id":4887398,"name":"Chicago","cod":200}
Read CSV file from the web
> iris_data = read.csv("https://archive.ics.uci.edu/ml/machine-learning-databases/iris/iris.data")
Scrape HTML tables from the web
If you want to scrape data from HTML tables in the web, you can use the htmltab package. To get the specific HTML table location , use xpath.
Once you get the xpath, use the following code
require(htmltab)
xpath = "//*[@id='mw-content-text']/div/table"
country_iso_codes = htmltab(doc = "https://simple.wikipedia.org/wiki/List_of_U.S._states",
which = xpath)
And you get a data frame
> country_iso_codes
Sl no. Abbreviation State Name Capital Became a State
2 1 AL Alabama Montgomery December 14, 1819
3 2 AK Alaska Juneau January 3, 1959
4 3 AZ Arizona Phoenix February 14, 1912
5 4 AR Arkansas Little Rock June 15, 1836