Exercise

Last observation carried forward (LOCF)

Another important imputation method is Last observation carried forward, or LOCF. This method works by filling in missing values with the most recent non-NA value that came before it.

In this exercise, you will impute a time series of a student's monthly examination scores, called monthly_test_scores. This dataset, along with the ggplot2 and zoo packages, are available to you.

Instructions

100 XP

  • Use last observation carried forward to impute missing values in monthly_test_scores; save this as monthly_scores_locf.

  • Complete the first autoplot() to generate a plot of the original monthly_test_scores time series.

  • Autoplot monthly_scores_locf with the 'minimal' theme, and the y-axis label "Examination Score (LOCF)".

  • Compare the plot of monthly_scores_locf with the plot of monthly_test_scores by switching between the plots.