How to Add a Count Column to a Data Frame in R

To add count column to data frame in R, you can use add_count() function from dplyr package.

The following method shows how you can do it with syntax.

Method 1: Use add_count() Function

library(dplyr)

df %>%
  add_count(column1, column2, name = "count")

The following example shows how to add count column to dataframe in R.

Using add_count() Function

Let’s see how we can add count column to dataframe using add_count() function:

library(dplyr)

# Create dataframe
df <- data.frame(Machine_name=c("A","B","C","D","E","F","G","H","A","B","A","C","D","B","E","H"),
                  Pressure=c(12.39,11.25,12.15,13.48,13.78,12.89,12.21,12.58,9.6,8.85,7.89,10.24,12.36,11.45,9.47,8.12))

# Add count column
df <- df %>%
  add_count(Machine_name, name = "count")

# Print dataframe
print(df)

Output:

   Machine_name Pressure count
1             A    12.39     3
2             B    11.25     3
3             C    12.15     2
4             D    13.48     2
5             E    13.78     2
6             F    12.89     1
7             G    12.21     1
8             H    12.58     2
9             A     9.60     3
10            B     8.85     3
11            A     7.89     3
12            C    10.24     2
13            D    12.36     2
14            B    11.45     3
15            E     9.47     2
16            H     8.12     2

Here the output shows new coolumn added to dataframe which having count of repeated elements in Machine_name column of dataframe.