# Count Number of Rows by Group Using dplyr Package in R (Example)

In this R tutorial you’ll learn how to get the number of cases in each group.

The article contains these topics:

Let’s take a look at some R codes in action…

## Introducing Example Data

As first step, we’ll have to define some data that we can use in the examples below:

```data <- data.frame(x1 = 1:10, # Example data x2 = letters[1:10], group = c("A", "A", "A", "B", "B", "B", "B", "C", "C", "D")) data # Show example data # x1 x2 group # 1 1 a A # 2 2 b A # 3 3 c A # 4 4 d B # 5 5 e B # 6 6 f B # 7 7 g B # 8 8 h C # 9 9 i C # 10 10 j D```

The previous output of the RStudio console shows the structure of our example data – It consists of three columns, whereby one of these columns is specifying the group of each row.

## Example: Find Number of Cases by Group Using group_by, summarise & n

This Example shows how to return a group counter using the dplyr package. First, we have to install and load the dplyr package:

```install.packages("dplyr") # Install dplyr package library("dplyr") # Load dplyr```

Now, we can use the group_by(), summarise() and n() functions to return a tibble containing all group counts:

```data %>% # Count rows by group group_by(group) %>% summarise(n = n()) # # A tibble: 4 x 2 # group n # <fct> <int> # 1 A 3 # 2 B 4 # 3 C 2 # 4 D 1```

As you can see based on the previous output of the RStudio console, group A has three cases, group B has four cases, group C has 2 cases, and group D has only 1 case.

## Video & Further Resources

Furthermore, you could read the related articles of this website. Some posts are shown below.

In summary: At this point of the post you should know how to count the number of rows within each group of a data frame in the R programming language. Let me know in the comments, if you have additional questions.