Regression with KNN

Now let's use KNN for a regression task. Let's use a person's height and sex to predict their weight. The following tables list our training and testing sets:

Height	Sex	Weight
158 cm	male	64 kg
170 cm	male	66 kg
183 cm	male	84 kg
191 cm	male	80 kg
155 cm	female	49 kg
163 cm	female	59 kg
180 cm	female	67 kg
158 cm	female	54 kg
178 cm	female	77 kg

Height	Sex	Weight
168 cm	male	65 kg
170 cm	male	61 kg
160 cm	female	52 kg
169 cm	female	67 kg

We will instantiate and fit KNeighborsRegressor, and use it to predict weights. In this dataset, sex has already been coded as a binary-valued feature. Notice that this feature ranges from 0 to 1, while the values of the feature representing the person's height range from 155 to 191. We will discuss why this is a problem, and how it can be ameliorated, in the next section. In the pizza price problem, we used the coefficient of determination to measure the performance of our model. We will use it to measure the performance of our regressor again, and introduce two more performance...