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  3. Writing Functions in Python

Exercise

Extract a function

While developing a model to predict college graduations, you wrote the code below to get the z-scores of students' yearly GPAs (z-scores indicate standard deviation from the mean). Now you're ready to turn it into a production-quality system, so you need to do something about the repetition. Writing a function to calculate z-scores would improve it.

# Standardize the GPAs for each year
df['y1_z'] = (df.y1_gpa - df.y1_gpa.mean()) / df.y1_gpa.std()
df['y2_z'] = (df.y2_gpa - df.y2_gpa.mean()) / df.y2_gpa.std()
df['y3_z'] = (df.y3_gpa - df.y3_gpa.mean()) / df.y3_gpa.std()
df['y4_z'] = (df.y4_gpa - df.y4_gpa.mean()) / df.y4_gpa.std()

Note: df is a pandas DataFrame where each row is a student with 4 columns of yearly student GPAs: y1_gpa, y2_gpa, y3_gpa, y4_gpa.

Instructions

100 XP
  • Finish the function so that it returns the z-scores of a column.
  • Use the function to calculate the z-scores for each year (df['y1_z'], df['y2_z'], etc.) from the raw GPA scores (df.y1_gpa, df.y2_gpa, etc.).