We might try at this point to keep adding features to our model in an attempt to increase its explanatory power.
For example, we also have a "Date of birth" column and we may be tempted to try and include this too. It is a date, but we could easily convert it into a number suitable for use in regression. We could do this simply by extracting the year from their birth date using the clj-time library:
(defn to-year [str]
(-> (coerce/from-date str)
(time/year)))
(defn ex-3-27 []
(let [data (->> (swimmer-data)
(i/add-derived-column "Dummy MF"
["Sex"]
dummy-mf)
(i/add-derived-column "Year of birth"
["Date of birth"]
to-year))
x (->> data
(feature-matrix ["Height, cm"
"Age"
"Dummy...