7.3: Accessing Data in Data Frames - Part ii

This is a continuation of the previous video.

Note: We should mention the very useful function subset() which allows us to extract subsets from data frames based on multiple logical tests. For example subset(cars, hp<150 & cyl<8). It is worth noting that the dataframe created by subset() will contain all factor levels of the original dataframe, even if some are not used - droplevels() can be used to remove unused levels.