Function Repository Resource:

GatherByIndex

Combine items into sublists based on their position

Contributed by: Bob Sandheinrich

ResourceFunction["GatherByIndex"][list,f]

gathers into sublists each set of elements in list that gives the same value when f is applied to its index.

Details and Options

ResourceFunction["GatherByIndex"] works only at the first level of list.

Gather consecutive characters using Mod:

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See which words Shakespeare's Mark Antony used at prime locations:

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This is data showing activity of requests on a server for each hour over several months:

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Stack each hour to show daily trends:

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MapIndexed uses the full part specification given as a List:

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GatherByIndex is applied to the index at the first level, so the position is not given as a List:

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