dplyr

Link to Databases

Let’s access an SQL database directly from R. Install the RSQLite package (and the dplyr package if you haven’t already).

Either use an existing copy of the portal_mammals.sqlite database or download a new copy. You should now be able to link to the surveys table in the database using:

surveys will be a tbl_df, which means that we won’t need to worry about it printing out huge numbers of rows in the answers below.

Using this table in the database:

1. Use the nrow() function to determine how many records are represented in this dataset.
2. Select the year, month, day, and species_id columns in that order
3. Create a new data frame with the year, species_id, and weight in kilograms of each individual, with no null weights.
4. Use the distinct() function to print the species_id for each species in the dataset that have been weighed.
5. Calculate the average size of a Neotoma Albigula (NL) in this dataset.
6. Create a new 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 I’d recommend checking out the dplyr vignette. Vignette’s can be a great way to learn how to use packages in R. If you’re in a hurry you can also do a search for count in the page.

[click here for output]