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Exercise

Understanding dummy variables

Selling craft beer is highly competitive. Increasing in-store visibility usually generates additional sales. Therefore, the brewery makes use of point-of-sales display ads. The volume sales of Hoppiness were recorded for all weeks with and without displays.

It is useful to start with examining log(SALES) separately for DISPLAY and no-DISPLAY activities. You can do this by using the function aggregate(). The aggregate() function can also operate on formula statements, a feature making its usage quite handy. Here, log(SALES) ~ DISPLAY groups log(SALES) according to the levels in DISPLAY. The function argument FUN applies a specified function to each level. Again, you calculate some simple descriptive measures using the functions mean(), min() and max().

Instructions
100 XP
  • Calculate the mean of log(SALES) for each level in DISPLAY.
  • Calculate the minimum of log(SALES) for each level in DISPLAY.
  • Calculate the maximum of log(SALES) for each level in DISPLAY.