Dr. Undómiel has decided to focus on the change in size of a few target rodent species over the course of the experiment(1977-2002). She has chosen Dipodymys spectabilis, Onychomys torridus, Perymiscus erimicus, Chaetodipus penicillatus.
Write a script that uses dplyr to:
portal_mammals.sqlite.year, species_id, and the average weight per 
year (avg_weight) for each target species. You may find the %in% c()
construction useful for your filter().copy_to() to include your new data frame in portal_mammals.sqlite. 
Call it something informative so that Dr. Undómiel can find it easily. Make
sure it remains after the connection is terminated using temporary = 
FALSE.