Pivot & Join

Being able to explode and pivot a compound field is great, but you are left with a dataframe of only those pivoted values. To really be valuable you'll need to rejoin it to the original dataset! After joining the datasets we will have a lot of NULL values for the newly created columns since we know the context of how they were created we can safely fill them in with zero as either the new has an attribute or it doesn't.

Este exercício faz parte do curso

Feature Engineering with PySpark

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Instruções do exercício

Pivot the values of ex_garage_list by grouping by the record id NO with groupBy() use the provided code to aggregate constant_val to ignore nulls and take the first value.
Left join piv_df to df using NO as the join condition.
Create the list of columns, zfill_cols, to zero fill by using the columns attribute on piv_df
Zero fill the pivoted dataframes columns, zfill_cols, by using fillna() with a subset.

Exercício interativo prático

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from pyspark.sql.functions import coalesce, first

# Pivot 
piv_df = ex_df.____(____).____(____).agg(coalesce(first(____)))

# Join the dataframes together and fill null
joined_df = ____.join(____, on='NO', how=____)

# Columns to zero fill
zfill_cols = ____.____

# Zero fill the pivoted values
zfilled_df = joined_df.____(0, subset=____)

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