Reducers are functions that tell the partition algorithm how
to reduce the data. as_reducer() is a helper function to create new
reducers to be used in partitioners. partitioners can be created with
as_partitioner().
reduce_scaled_mean() returns the scaled row means of the
target variables to reduce.
reduce_scaled_mean(.partition_step)a partition_step object
Other reducers:
as_reducer(),
reduce_first_component(),
reduce_kmeans()