R Count Number of Cases within Each Group – dplyr Package (Example Code)
In this tutorial you’ll learn how to count the number of rows within each group of a data frame in R.
Example Data
data(iris) # Iris data set head(iris) # Sepal.Length Sepal.Width Petal.Length Petal.Width Species # 1 5.1 3.5 1.4 0.2 setosa # 2 4.9 3.0 1.4 0.2 setosa # 3 4.7 3.2 1.3 0.2 setosa # 4 4.6 3.1 1.5 0.2 setosa # 5 5.0 3.6 1.4 0.2 setosa # 6 5.4 3.9 1.7 0.4 setosa |
data(iris) # Iris data set head(iris) # Sepal.Length Sepal.Width Petal.Length Petal.Width Species # 1 5.1 3.5 1.4 0.2 setosa # 2 4.9 3.0 1.4 0.2 setosa # 3 4.7 3.2 1.3 0.2 setosa # 4 4.6 3.1 1.5 0.2 setosa # 5 5.0 3.6 1.4 0.2 setosa # 6 5.4 3.9 1.7 0.4 setosa
Example: Counting Number of Cases within Each Group
install.packages("dplyr") # Install & load dplyr library("dplyr") |
install.packages("dplyr") # Install & load dplyr library("dplyr")
iris %>% # Identify number of rows rows by group group_by(Species) %>% summarise(n = n()) # # A tibble: 3 x 2 # Species n # <fct> <int> # 1 setosa 50 # 2 versicolor 50 # 3 virginica 50 |
iris %>% # Identify number of rows rows by group group_by(Species) %>% summarise(n = n()) # # A tibble: 3 x 2 # Species n # <fct> <int> # 1 setosa 50 # 2 versicolor 50 # 3 virginica 50