dplyr

Collect from Databases

This is a follow-up to Link to Databases.

Make sure you have an existing copy of the portal_mammals.sqlite database or download a new copy.

Notice how the solution to Link to Databases task 4 is a <derived table> and that the number of rows is unknown (??).

1. Take this <derived table> and make it a local data frame using collect() and determine how many rows it has.
2. Calculate the average size of a Neotoma Albigula (NL) in surveys and store the result in a local data frame.
3. Create a local data frame with the number of individuals counted in each year of the study. If you don’t know how to count things using dplyr, take another look at the dplyr vignette. Vignettes are a great way to reference packages in R if you don’t know the name of a function you need but you know the package has that capability. In this case, you will want to search for ‘count’.

Want a challenge?: Create a local data frame containing the average size of each rodent species for individuals captured on the Control plots. You can do this by either creating a connection to the species and plots tables and using inner_join in dplyr or by writing the query in SQL and using tbl(portaldb, sql(query)), where query is a string containing the SQL you want to run. Better yet try doing it both ways.

[click here for output]