GroupBy a list of associations with their keys

Question

How can I go from

as =  {
    <|A->{1,11},B->{1,12},C->{1,13}|>,
    <|A->{2,21},B->{2,22},C->{2,23}|>,
    <|A->{3,31},B->{3,32},C->{3,33}|>
}

to

<|
     "A" -> {{1, 11}, {2, 21}, {3, 31}}, 
     "B" -> {{1, 12}, {2, 22}, {3, 32}}, 
     "C" -> {{1, 13}, {2, 23}, {3, 33}}
|>

I think I should use some variation of GroupBy[as,condition] but I can't really figure out what condition should be.

No need for the version-10 tag; that is implied by the use of Association. — Mr.Wizard, Sep 29 '14 at 16:24

score 15 · Accepted Answer · answered Sep 29 '14 at 16:27

15

This operation is performed by Merge:

Merge[as, Identity]

<|A -> {{1, 11}, {2, 21}, {3, 31}},
  B -> {{1, 12}, {2, 22}, {3, 32}}, 
  C -> {{1, 13}, {2, 23}, {3, 33}}|>

answered Sep 29 '14 at 16:27

Mr.Wizard

score 9 · Answer 2 · answered Sep 29 '14 at 16:42

9

Another approach:

AssociationThread[Keys[as][[1]], Transpose@Values[as]]

<|A -> {{1, 11}, {2, 21}, {3, 31}},
  B -> {{1, 12}, {2, 22}, {3, 32}}, 
  C -> {{1, 13}, {2, 23}, {3, 33}}|>

answered Sep 29 '14 at 16:42

RunnyKine

score 3 · Answer 3 · answered Sep 29 '14 at 16:34

3

GroupBy[Catenate @ Normal @ as, First -> Last]

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answered Sep 29 '14 at 16:34

eldo

3 Answers3