by using #3,#3-1,#3-2,#3-3, solve only #3-4(fill in the "???" part) those are R scripts

# Question 3 #data import data("iris") # 3-1) # Compute the average of "sepal . Length" for each species mean_of_species mean_of speciesSx[1]) idx-versicolor mean_of-species$XL2D idx-virginica