Identifying outliers and extreme values in bivariate relationships
It is hard to develop a reliable model without having a good sense of the bivariate relationships in our data. We not only care about the relationship between particular features and target variables but also about how features move together. If features are highly correlated, then modeling their independent effect becomes tricky or unnecessary. This may be a challenge, even if the features are highly correlated over just a range of values.
Having a good understanding of bivariate relationships is also important for identifying outliers. A value might be unexpected, even if it is not an extreme value. This is because some values for a feature are unusual when a second feature has certain values. This is easy to illustrate when one feature is categorical and the other is continuous.
The following diagram illustrates the number of bird sightings per day over several years but shows different distributions for the...