Import packages
library(plyr) # loading plyr for mutate function
Subset only setosa species from Iris
iris_setosa <- subset(iris, Species == "setosa")
paste("Unique species in iris_setosa:", unique(iris_setosa$Species), sep = " ")
## [1] "Unique species in iris_setosa: setosa"
levels(iris_setosa$Species)
## [1] "versicolor" "setosa" "virginica"
Levels shows all species even though filtered dataset only contains setosa
Removing versicolor and virginica species from the filtered dataset
iris_setosa$Species <- droplevels(iris_setosa$Species)
levels(iris_setosa$Species) # levels of iris_setosa are correctly reflected