DOCUMENTATION CENTER SEARCH

Mathematica > Core Language > List Manipulation > Rearranging & Restructuring Lists >

Built-in Mathematica Symbol

GatherBy

GatherBy[list, f]
gathers into sublists each set of elements in list that gives the same value when f is applied.

GatherBy[list, {f₁, f₂, ...}]
gathers list into nested sublists using f_i at level i.

GatherBy[{e₁, e₂, e₃, ...}, f] evaluates f[e_i] for each i to determine how to gather the e_i.

Within each sublist generated by GatherBy[list, ...], elements appear in the same order as in list; the complete sublists are ordered so that their first elements appear in the same order as in list.

GatherBy[list] is equivalent to GatherBy[list, Identity], which is also equivalent to Gather[list]. »

GatherBy[list, {f₁, f₂}] is equivalent to Map[GatherBy[#, f₂]&, GatherBy[list, f₁]].

Gather data in odd and even lists:

Gather by remainder:

Gather by the first component in a vector:

Gather dates by year:

Gather by the first component and within that, gather by the last component:

Use Framed to display grouping: