R Extract Top N Highest Values of Column by Group (Example Code)

In this tutorial, I’ll explain how to extract the N highest values within each group of a data frame column in the R programming language.

Example Data

data(iris)                                       # Loading iris
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: Select Top N Highest Values of Data Frame Column by Group

iris_highest <- iris[order(iris$Sepal.Length,    # Sorting values of data
                           decreasing = TRUE), ]
iris_highest <- Reduce(rbind,                    # Extracting highest values by group
                       by(iris_highest,
                          iris_highest["Species"],
                          head,
                          n = 2))
iris_highest                                     # Showing updated data in RStudio
#     Sepal.Length Sepal.Width Petal.Length Petal.Width    Species
# 15           5.8         4.0          1.2         0.2     setosa
# 16           5.7         4.4          1.5         0.4     setosa
# 51           7.0         3.2          4.7         1.4 versicolor
# 53           6.9         3.1          4.9         1.5 versicolor
# 132          7.9         3.8          6.4         2.0  virginica
# 118          7.7         3.8          6.7         2.2  virginica

Further Resources & Related Articles

Below, you may find some additional resources on topics such as counting and groups.

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