Gather data in odd and even lists:

Gather by the first part:

Gather by remainder:

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

Use Framed to display grouping:

Define a GatherBy operator:

Use the operator to gather integer data, putting each group on a separate row of a column:

Use the operator to gather string data:

Create a list of associations:

Gather by the value of the key "a":

Gather by the values of the keys "a" and "b", using the operator form of GatherBy:

Sort and then gather strings by their first letters:

Gather dates by year:

Simulate some data:

Group elements based on the value of the second element:

Count the number of data points in each group:

Compute the means of the third element by group:

Group machine numbers by equivalence class based on rounding off the last tol bits:

Generate an unordered sample of distinct machine numbers close to 1:

Gather by equivalence class:

See how the factors in were grouped:

Here are the equivalence representatives and the values such that :

GatherBy[list,Identity] is equivalent to Gather[list]:

GatherBy[list,f] is equivalent to Gather[list,(f[#1]===f[#2])&]:

Display the groups along with the norm of each group:

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

GatherBy[f][list] is equivalent to GatherBy[list,f]: