Preprocessing numeric features

What would have happened if you had included the with 'with_missing' column in the last exercise? Without imputing missing values, the pipeline would not be happy (try it and see). So, in this exercise you'll improve your pipeline a bit by using the Imputer() imputation transformer from scikit-learn to fill in missing values in your sample data.

By default, the imputer transformer replaces NaNs with the mean value of the column. That's a good enough imputation strategy for the sample data, so you won't need to pass anything extra to the imputer.

After importing the transformer, you will edit the steps list used in the previous exercise by inserting a (name, transform) tuple. Recall that steps are processed sequentially, so make sure the new tuple encoding your preprocessing step is put in the right place.

The sample_df is in the workspace, in case you'd like to take another look. Make sure to select both numeric columns- in the previous exercise we couldn't use with_missing because we had no preprocessing step!

Import Imputer from sklearn.preprocessing.
Create training and test sets by selecting the correct subset of sample_df: 'numeric' and 'with_missing'.
Add the tuple ('imp', Imputer()) to the correct position in the pipeline. Pipeline processes steps sequentially, so the imputation step should come before the classifier step.
Complete the .fit() and .score() methods to fit the pipeline to the data and compute the accuracy.

Exercise

Preprocessing numeric features

Instructions