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Gather

Gather[list]
gathers the elements of list into sublists of identical elements.
Gather[list, test]
applies test to pairs of elements to determine if they should be considered identical.
  • The default function used to test whether elements are identical is SameQ.
  • Gather[{e1, e2, ...}, p] will gather together elements for which p[ei, ej] returns True.
EXAMPLESCLOSE ALL
Basic Examples   (4)
Gather multiple solutions together:
Gather elements that have equal integer parts:
Gather integers that have identical remainders:
Gather polynomials that have identical remainders:
Check the remainders in each list:
Gather multiple solutions together:
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Gather elements that have equal integer parts:
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Out[1]=
 
Gather integers that have identical remainders:
In[1]:=
Click for copyable input
Out[1]=
 
Gather polynomials that have identical remainders:
In[1]:=
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Out[1]=
In[2]:=
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Out[2]=
Check the remainders in each list:
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Out[3]=
Properties & Relations   (2)
DeleteDuplicates[list] is equivalent to Gather[list][[All, 1]]:
For a large list, DeleteDuplicates is much faster:
GatherBy[list, f] is equivalent to Gather[list, (f[#1]SameQf[#2])&]:
Gather the rows by Norm and display with the common norm of each group:
Compare to the result of Gather:
Possible Issues   (1)
When the test cannot be identified as a equality comparison, Gather may be much slower:
The results are identical:
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