How to Extract the Column Index in a Data Frame by Its Label in R (Example Code)

This page explains how to identify the variable index based on its label in a data frame in R programming.

Creation of Example Data

data(iris)                                 # Load iris data frame
head(iris)                                 # Head of data
#   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: Returning Column Index of Matching Variable

which(colnames(iris) == "Petal.Length")    # Applying which function
# 3

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