Wolfram Function Repository

Instant-use add-on functions for the Wolfram Language

Function Repository Resource:

 Duplicates

Source Notebook

Select all the elements that appear twice or more in a list

Contributed by: Sander Huisman

ResourceFunction["Duplicates"][list]

gives back the elements that appear twice or more in list.

Details and Options

Results are given back in the order of first appearance.

Examples

Basic Examples (2) 

Only the repeated elements (1 and 2) are returned:

In[1]:=
ResourceFunction["Duplicates"][{1, 2, 1, 2, 3, 4, 5, 1}]
Out[1]=
Image

Duplicates looks at elements at level 1:

In[2]:=
ResourceFunction[ "Duplicates"][{{1, 1}, {2, 1}, {1, 1}, {2, 2}, {3, 1}, {4, 4}, {4, 3}, {2, 2}}]
Out[2]=
Image

Properties and Relations (2) 

Duplicates gives all the copies of the repeated elements:

In[3]:=
ResourceFunction["Duplicates"][{1, 2, 1, 2, 3, 4, 5, 1}]
Out[3]=
Image

Use the resource function DuplicatesList to get the unique elements:

In[4]:=
ResourceFunction["DuplicatesList"][ ResourceFunction["Duplicates"][{1, 2, 1, 2, 3, 4, 5, 1}]]
Out[4]=
Image

Possible Issues (1) 

An empty list is returned if there are no duplicates:

In[5]:=
ResourceFunction["Duplicates"][Range[10]]
Out[5]=
Image

Publisher

SHuisman

Version History

  • 1.0.0 – 11 March 2020

Related Resources

License Information