This is a follow-up to Connect and Query.
Dr. Undómiel agrees with you that the difference in male and female D. spectabilis hind foot length and weight seems pretty small, but wants to have a reference point for comparison. She wants you to find the male and female hind foot length and weight for all species of rodent on all of the plots (not just the controls).
Produce a data frame with species_id, sex, avg_hindfoot_length, and
avg_weight for each species. Your data frame should have two rows for each
species, one row for each sex.
You can solve this problem in a variety of ways including using dplyr, a
GROUP BY in your SQL query, a for loop, or using apply statements. Take
whichever approach you like best.