What is tidyr gather function in R?

If we need to gather a key-value pair from the specified columns then the gather() function in tidyr is used. It is deliberated as one of the core methods in R language. gather() is used when any column is not variable. Thus, it is quite a useful function for creating tidy data.

gather() function in R is used to merge multiple columns of the same values into a single while ungroup() function is used exactly in the opposite meanings.

Syntax

gather(data, key value, …)

Parameters

• data: It contains the name of the data frame.
• key: It shows the name of the key column which is to be created.
• value: It depicts the name of the value column to be created.
• …: It shows the columns we need to gather the key-value pair.

Example 1

We are going to discuss an example regarding the gather() method.

#creating a data frame
df <- data.frame(Candidate=c('John', 'Topley', 'Brook', 'Smith','Miley'),
                 Maths=c(55, 84, 86, 99,100),
                 Stats=c(99, 85, 78, 98,79))
#printing data frame
print(df)
library(tidyr)
#gathering data across columns 2nd and 3rd
gather(df, key="Subject", value="Marks", 2:3)

• Line#2-4: here we have created a data frame df.
• Line#6: print the data frame df on the console.
• Line#7: here we have called the tidyr library.
• Line#9: it shows the usage of the gather() function to create key-value pairs by using 2nd and 3rd columns.

Example 2

Now we are going to discuss the example where we will gather values by using more than two columns.

#creating a data frame
df <- data.frame(Candidate=c('John', 'Topley', 'Brook', 'Smith','Miley'),
                 Maths=c(55, 84, 86, 99,100),
                 Stats=c(99, 85, 78, 98,79),
                 Economics=c(45,67,87,75,68))
#printing data frame
print(df)
library(tidyr)
#gathering data across columns 2nd and 3rd
gather(df, key="Subject", value="Marks", 2:4)

• Line#2-5: here, we have created a data frame df.
• Line#7: printing data frame df on the console.
• Line#8: here we have called the tidyr library.
• Line#10: shows the use of the gather() function to create key-value pairs using the 2nd, 3rd, and 4th columns. Then two new columns, namely Subject and Marks, are created by gathering the values of 2, 3, and 4 columns.