Import Data in R Programming

In this tutorial, you will learn about how to import (read) data from various sources such as txt file, csv (comma-separated values)  files. The data scientist usually stores data in Excel Spreadsheets. In the R programming language, there are several R packages such as XLConnect, xlsx, RExcel, gdata, RODBC, etc to access the data from Excel Spreadsheets. The R users or programmers save the spreadsheets (data) mostly in CSV format/files to take advantage of R‘s built-in functionalities to manipulate the data. So through this tutorial, you will learn the read (import)  from .csv files in R language.

How to import data in R?

We need data to process our requirement, these data are read or imported into your program from spreadsheets or from any other sources for data analysis. The Microsoft Excel Spreadsheet is one of the most common ways to import data into R using a CSV file (Comma Separated Variable file). You can save your spreadsheet as a CSV file by making a copy of the same file and saving it in .csv file format. Let us see step by step how is spreadsheet converted to a .csv file type works with the R program. 

1. The Microsoft Excel Spreadsheet shows the area and price related to houses. For example, the first column is an area, which provides the information that if the area is 2600 then the house price will be 550000 and so on with some other areas and their relating house price.
   
2. Right-click the file name. You can find option properties. Click properties a box opens showing the details of file type. Here you can see the file type as .xlsx (Microsoft Excel Worksheet).
   
3. The file type needs to be changed to a .csv file from the .xlsx file type. In order to do that make a copy of the same file and save the file with the .csv extension.Once you change the file type. Again take properties and view the file type.
   
4. You can view the same files(3-1 home prices) with two file types(Microsoft Excel Comma Separated Values file (csv) and  Microsoft Excel  Worksheet (.xlsx) in your folder if both files are located in the same folder.
   

Importing /Reading csv file

There is some basic knowledge needed to know before reading a file into the R program. They are  as listed below

1. The file to import/read must be located in the current working directory then only it can be accessed /read by the R program. The current working directory of R can be checked using getwd() function.
2. In case our file is located in any different location, it can be accessed or read from that location by setting it as the current working directory. The setwd() function enables to set the current working directory.
3. Once the file is available in the current working directory of R, you can read the file using the read.csv() function. 
4. The read.csv() reads the file in table format and creates a data frame from it as an output. As we discussed in our data frame tutorial, a data frame is a datatype of the two-dimensional array for storing the data tables.

getwd()
[1] "C:/Users/John/Documents"
 

Suppose you need to change the current working directory because your file to read is saved under some other directories using setwd() function. The same can be done in RStudio by following the below steps

• Click Session in RStudio
• Click set the working directory
• Click choose directories

By choosing the file location you can change and set your current working directory.

Import data using the RStudio interface

One of the easiest ways to import datasets to the R program is using the import Dataset option in RStudio. 

For importing text files use the first option from where you can browse and open the text file.

You can change the name of the dataset from here. Also, other options such as heading, row names, etc can be altered based on user requirements.

Click the Import button to load the dataset into the R program. You can view the same dataset loaded into Rscript. The object named 3-1homeprices gets created in a global environment.

How to import .csv file using read.csv() method?

The R program allows loading the .csv file type into the workspace using a built-in method known as read.csv() or by loading or importing external packages and storing them as data frames (df). The method read.csv() is included in base R supports to load data to R script and execute the program.

In the below example the read.csv() function is used to load the data in the .csv file type with file name 3-1homeprices.You can specify the entire file path such as “C:\\Users\\Desktop\\R\\R Pgms\\3-1homeprices.csv" to load the data as long as the .csv file is saved in the same folder as your R script.

######importing Data ######
####using read.csv() ######
df1=read.csv(file ="C:\\Users\\Desktop\\R\\R Pgms\\3-1homeprices.csv" )
print(df1)

When the above piece of code is executed the data stored in the file gets displayed as

print(df1)
  area  price
1 2600 550000
2 3000 565000
3 3200 610000
4 3600 680000
5 4000 725000

Compare the contents of data displayed in the R console with spreadsheet data, both are similar. So using the read.csv() function you can easily pull spreadsheet data into the R program. Look at the below screenshot.

In the RStudio, you can view the data by clicking on df1 variable in Environment(right panel), which shows 5 observations of two variables as area and price in the left panel.

In the above example, we provided the full path in one step to read the data into a data frame named df1. This can be also achieved by mentioning the path in another step and just calling the path inside the function read.csv(). The syntax it follows is given below

read.csv(path, header = TRUE, sep = “,”)
 

Arguments :

• path: The path of the file to be imported
• header: By default : TRUE . Indicator of whether to import column headings.
• sep = “,” : The separator for the values in each row.

Example:  Specifying path and calling inside read.csv()

The path “C:/Users/Desktop/R/R Pgms/3-1homeprices.csv” where the file resides is specified in a separate line by storing to a variable named path. When there is a requirement for loading a dataset simply call the name of the variable where the path is stored. In our example, the variable path holds the details of .csv location. 

#path specifying
path = "C:/Users/Desktop/R/R Pgms/3-1homeprices.csv"

#loading data from .csv file
data = read.csv(path)

#Displays the data
print(data)

 

The code when executed fetches the data stored in .csv file as

area  price
1 2600 550000
2 3000 565000
3 3200 610000
4 3600 680000
5 4000 725000

In case if the header is set to FALSE in the syntax ,the column header names area, prices will not be displayed. It will by default represent as V1,V2…etc depending upon the number of columns in the dataset

#path specifying
path = "C:/Users/Desktop/R/R Pgms/3-1homeprices.csv"


#loading data from .csv file with columns names are hidden
data = read.csv(path,header = FALSE)

#Displays the data
print(data)

 

The output will not specify the column names

V1     V2
1 area  price
2 2600 550000
3 3000 565000
4 3200 610000
5 3600 680000

You are going to learn about two packages in R, readr and data.table.We will begin with setting the location or directory where the files or data resides using setwd() function.

Make sure to install the packages using the following commands

install.packages("readr")
#to load readr library

install.packages("data.table")
#to load data.table  library
 

The screenshot gives the idea of working directory setup and installation of packages and importing the library using library() function with the name of the package to be imported inside the parentheses as arguments.

The readr library is created by the authors Madley, Jim, and Romain. The read.csv() function under readr package with some default arguments is used to load or import data.

The whole data is read by giving the path and the object is stored as data.Two functions head() and str() further used whose output is as given in below screenshot.

data = read.csv(file ="C:\\Users\\Desktop\\R\\R Pgms\\3-1homeprices.csv")
head(data)
str(data)

How to Import an text file into R?

The read.table() function is used to import text files into R program

df2= read.table(file ="C:\\Users\\Desktop\\R\\R Pgms\\3-1homeprices1.txt")
print(df2)

 

The output is

You can see there is more than one column in dataframe with V1,V2 above the columns.You can set header argument equals to TRUE to set the column names as actual headers insead of V1,V2 etc.

df2= read.table(file ="C:\\Users\\Desktop\\R\\R Pgms\\3-1homeprices1.txt",header = TRUE)
print(df2)
 

The output is given below where the V1,V2 is vanished with the headers area and price .