How to Extract the First Row by Data Frame Group in R (Example Code)

This tutorial illustrates how to return the top line of each data table group in the R programming language.

Creating Example Data

data(iris)                           # Load & inspect first rows of data
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: Return First Row within Each Group of Iris Data Frame

iris[!duplicated(iris$Species), ]    # Using duplicated function in R
#        Sepal.Length Sepal.Width Petal.Length Petal.Width Species
# 1            5.1         3.5          1.4         0.2     setosa
# 51           7.0         3.2          4.7         1.4 versicolor
# 101          6.3         3.3          6.0         2.5  virginica

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