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Filtering grouped data? #315

Closed xinkai-zhou closed 4 years ago

xinkai-zhou commented 4 years ago

Hello, I couldn't filter on grouped data, did I missing anything?

using DataFrames, Query
df = DataFrame(a = repeat([1, 2, 3, 4], outer=[2]),b = repeat([2, 1], outer=[4]),c = 1:8)
df |>@groupby(_.a) |> @filter(_.a == 1)

This gives ?-element query result.

xinkai-zhou commented 4 years ago

The following approach works:

df |> @groupby(_.a) |> @filter(key(_) .∈ Ref(Set([1, 2])))