R Programming By Example

Adding a third dimension with colors

As often happens, we want to work on some code we had already created to add more features. In this case, we want to add a third dimension to the graphs using colors. We want to be able to specify a color variable that will be used to further divide the data in the graph.

To accomplish this, we add a color parameter to the function's signature using the "NULL check" pattern and we add the corresponding parameter in each case. Adding the parameter directly in the aes_string() function is not problematic in case of NULL because NULL values indicate to ggplot() we don't want to use a fill color for the graph.

However, note that we are not able to use the same technique with y . Instead, we check whether we ...