Conditional union of a nested list

Question

With a nested list such as

listA = {{{a,b,c},{1,0,0}}, {{a,b,c},{0,1,0}}, {{d,e,f},{1,1,0}}};

How can I create

listB = {{{a,b,c},{{1,0,0},{0,1,0}}}, {{d,e,f},{1,1,0}}};

and so-forth for any length of listA?

At least closely related: https://mathematica.stackexchange.com/q/4332/5478 — Kuba, Feb 24 '18 at 22:52

kglr · Accepted Answer · 2018-02-24T22:58:50.927

7

KeyValueMap[List] @ GroupBy[listA, First -> Last] 
Values @ GroupBy[listA, First, {#[[1, 1]], #[[All, 2]]}&] 
KeyValueMap[List] @ Merge[Association /@ Rule @@@ listA, Identity]
{#[[1, 1]], #[[All, 2]]} & /@ GatherBy[listA, First]

all give

{{{a, b, c}, {{1, 0, 0}, {0, 1, 0}}}, {{d, e, f}, {{1, 1, 0}}}}

edited Feb 24 '18 at 22:58

answered Feb 24 '18 at 22:43

kglr

394,356
18
477
896

Very nice and concise. And general! – Phillip Dukes Feb 24 '18 at 22:49
@PhillipDukes, thank you for the accept. – kglr Feb 24 '18 at 22:59

Conditional union of a nested list

1 Answers1