FAQ: Aggregates in R - Combining Grouping with Filter

This community-built FAQ covers the “Combining Grouping with Filter” exercise from the lesson “Aggregates in R”.

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FAQs on the exercise Combining Grouping with Filter

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I know we are filtering based on a groups aggregate statistic, and returning only the values where that is true (so, only the groups where that is true). It makes sense to me that the actual aggregate that we use to filter does not affect the values in the data frame (it isn’t applied to them, only to select them).

However, can anyone help me understand why the groups we create with group_by() aren’t maintained, even after filtering?

Like, in this exercise we group the orders data frame by shoe_type, then filter out the groups that aren’t popular (under 16 sales total).

But, in our final table that we make, the data frame is no longer grouped by shoe_type. I can see that only the boots, sandals, and wedges are present (the popular groups), but I would have expected ALL the boots, then ALL the sandals, then ALL the wedges after the group_by command.

Am I misunderstanding something with group_by() and the “sub-categories” it creates?
Is this R being intelligent for us, knowing that we probably don’t want those groups?

I’m implementing this fine, but I’d appreciate any guidance you might have to assist my conception of this.

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I just came across this exercise and had the same doubt, too bad nobody from Codecademy has given an answer for this topic…