Okay, we’ve covered how to load a data file into Tableau. But what if a single data file doesn’t have all the variables we need to answer a question?
Maybe we have all the data we need but it’s in multiple files or tables. Tableau allows us to use data from multiple files using its Relationship feature to automatically (or manually) join files on a common field.
Sticking with our Tree Census dataset, let’s say we wanted to be able to show whether trees are native species or not. If we just so happen to have a dataset with each tree’s Latin name and its native species status, we can do just that! All we have to do in Tableau is ensure that the two tables form a Relationship based on their shared column.
- Download the Tree Species data set and save it in the same folder as your
Tree Censusdata file.
- Click the
Data Sourcetab on the left bottom of your screen.
- In the File sidebar, you will see your
tree_species_nyc.csvsource. Drag that file and drop it next to the Tree census box. You will see an orange “noodle” that is showing us a relationship can be made. It will look like we made an error, but don’t be alarmed.
- Your data sources have a common field, but they don’t share the same name, so Tableau isn’t sure how to join these two. We can fix this by manually assigning which fields Tableau uses. Go to the
Select a fieldoption in the bottom left of your window.
- In the left dropdown select
Spc Latin. In the right dropdown select
Scientific name. This should remove the error so that you can explore the data from both sources. Look at that! Now we’ve got access to all the information from both datasets!