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Results tagged with gathering
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user 1997
Questions on gathering, grouping or clustering data based on certain criteria. This is to be used with primary tags such as list-manipulation, string-manipulation or similar tags, with the primary tag indicating the specific use case.
0
votes
Summarize a list of pairs / (Using GatherBy and Tally?)
An approach using Reap and Sow:
Using:
lst = {{"games", "minecraft"}, {"games", "minecraft"}, {"games",
"WoW"}, {"books", "book1"}, {"books", "book1"}, {"books",
"book1"}, {"books", "book5"} …
- 64.9k
4
votes
Replace a set of vectors in a list from another set of vectors
Perhaps (apologies if I have misinterpreted):
A /. ({_, #[[2]], __} -> # & /@ B)
- 64.9k
4
votes
Simple way to group the list-indices of equal elements?
You can also used Reap/Sow, e.g.
pi[u_] := Reap[MapIndexed[Sow[#2[[1]], #1] &, u]][[2]]
So pi[{f, f, g, g, f}] yields
{{1, 2, 5}, {3, 4}}
- 64.9k
5
votes
Gather list elements by labels
This also works:
Reap[MapThread[Sow, {list, labels}]][[2]]
or an alternatively ordering by tags:
Reap[MapThread[Sow, {list, labels}], Union @ labels][[2, All, 1]]
- 64.9k
2
votes
Group matrix values by column
I am not sure I understand. Here are some ways to group by last element:
list={{1, 1}, {1, 3}, {2, 1}, {2, 2}, {2, 3}}
GatherBy[list, Last]
GroupBy[list, Last]
Last@Reap[Sow[{##}, #2] & @@@ list, _, …
- 64.9k
2
votes
GatherBy based on condition imposed on index variable
Just for fun:
Join @@@ ({{1, 2}, {3, 4, 5}, {6}} /.Last@Reap[Sow[{##}, #1] & @@@ testdat, _, Rule])
yields:
{{{1, a11, b11}, {1, a12, b12}, {2, a21, b21}, {2, a22, b22}}, {{3,
a31, b31}, {3, a …
- 64.9k