Let's do a quick exercise to get practice with that groupby function. First, make sure that you've imported stock data CSV into the data frame stock data. And then very quickly you should be able to calculate that mean aggregation function for all of the features in stock data by industry sector.

To accomplish this, we just write one very quick and easy line of code, so stock data, the name of our data frame, and then dot groupby the groupby function. And then we just pass one argument, which is the feature by which we are grouping our data set, and in this case it's the feature sector. And then after that we are using the mean aggregation function. So dot mean when I execute that cell, it's going to split the data into all of these different sectors and then it'll give us the mean of all of our different features.