Is there a function in the standard library simila...

# announcements

[Luke]

Is there a function in the standard library similar to groupBy but returns a List<List<T>> instead of a map? I don’t need the keys.

[nfrankel]

i guess you can just get the values from the map

[Fleshgrinder]

.groupBy { … }.values https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.collections/-map/values.html

[Luke]

Yes well… That’s what I am doing right now, but that’s an extra step. I don’t need an extra map creation

[Fleshgrinder]

Directly collect into a set then.

[Fleshgrinder]

It's hard to give a proper answer because it's not exactly clear what data you have and what data you want. 😉

[Luke]

I have a list of models with a timestamp that I am grouping per day, but the day is irrelevant.

[Fleshgrinder]

So you want a list with lists containing the models per day. I fail to see how this is possible without keeping track of something… I guess some math magic is possible if the amount of days we go back is limited and we use an outter array with a fixed length… this is getting out of hand already. I think the intermediate map is a good middle ground. How would you solve it without keeping track of anything?

[Luke]

Smart observation. All right I’ll keep it the way it is. Thanks for your hindsight

[arekolek]

~h~in~d~sight

FTFY

[Fleshgrinder]

🙂

[jimn]

@Luke what is the overall usecase? i've been refining a dataframe focussed on timeseries resample+pivot+groupby workloads and came upon groupby using indexes mapped into [the same as] List<List<*>> as an transform of an immutable source