Grouping Lists of lists based on revit paramter values

I am trying to group elements in a list using the List.GroupByKey node but I am having problems using this for sublists.

As can be seen below I am collecting all Analytical Floor Elements.

I am then grouping this based on the values of a “Level/Zone” parameter, using the List.GroupByKey node, works all OK.

For each of these sublists I wish to group by another parameter. I feel as though I should be using the List.Map node because you use this node to work on sublists but this is not working.

The Clockwork Package has a List.GroupListOfListByKey node but I am having trouble getting this to work. (not sure which key index to pass to it)


Group sublists.dyn (13.6 KB)

Would love some help solving this.


Hi Brett,

I hope this is helpful:

First the cable trays are grouped by Reference Level which gives me 4 sublists. Then i group them by Family.

Kind regards

Thanks Martin,

Getting me closer but not 100% there.

I was able to use the group by function key and feed it into node for the second parameter key so that it applies to the sublists but I can’t get it to work when using a nested second parameter.

The top row is when I have nested parameter feeding into the second group by function. If you see the output on the RHS I’m not getting sublists with unique keys.

Where as when I only feed one parameter key into the group by function I am getting unique keys for the sublist.

Hope this explains my problem

Seems like List.Combine should help


Vikram, thanks very much!

It always seems so obvious when the correct answer is shown to you.


This was my solution to the problem Thankyou very much!!

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I’ve been trying to solve this problem for hours now and you finally gave me the solution. I cannot thank you enough lol.

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Great solution, thanks! Never would have solved it on my own. Works also for geometry.