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DeleteAdjacentDuplicates
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DeleteAdjacentDuplicates

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deletes all duplicates in runs of identical elements in list.

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applies test to pairs of consecutive elements to determine whether they should be considered duplicates.

Details

Examples

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Basic Examples  (3)Summary of the most common use cases

Delete adjacent duplicated elements:

In[1]:=1
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https://wolfram.com/xid/0comb7n1edjgqokiumqk-23ar61
Out[1]=1

Delete adjacent elements that coincide under Equal:

In[1]:=1
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https://wolfram.com/xid/0comb7n1edjgqokiumqk-gwgu24
Out[1]=1

Delete elements whose values duplicate those just before them in the association:

In[1]:=1
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https://wolfram.com/xid/0comb7n1edjgqokiumqk-9lj38k
Out[1]=1

Scope  (2)Survey of the scope of standard use cases

Delete elements unless they are larger than the preceding ones:

In[1]:=1
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https://wolfram.com/xid/0comb7n1edjgqokiumqk-uoelt8
Out[1]=1

In DeleteAdjacentDuplicates[list], list may be any nonatomic expression:

In[1]:=1
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https://wolfram.com/xid/0comb7n1edjgqokiumqk-co5up
Out[1]=1

Properties & Relations  (2)Properties of the function, and connections to other functions

DeleteAdjacentDuplicates is similar to taking the first of each item from Split:

In[1]:=1
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https://wolfram.com/xid/0comb7n1edjgqokiumqk-jv1mup
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0comb7n1edjgqokiumqk-dfkds3
Out[2]=2
In[3]:=3
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https://wolfram.com/xid/0comb7n1edjgqokiumqk-brto0x
Out[3]=3

Delete sublists that have the same total:

In[1]:=1
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https://wolfram.com/xid/0comb7n1edjgqokiumqk-k2fvx7
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0comb7n1edjgqokiumqk-neboqu
Out[2]=2

The equivalent operation can be achieved using SplitBy as well:

In[3]:=3
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https://wolfram.com/xid/0comb7n1edjgqokiumqk-grxnwx
Out[3]=3
Wolfram Research (2022), DeleteAdjacentDuplicates, Wolfram Language function, https://reference.wolfram.com/language/ref/DeleteAdjacentDuplicates.html.
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Wolfram Research (2022), DeleteAdjacentDuplicates, Wolfram Language function, https://reference.wolfram.com/language/ref/DeleteAdjacentDuplicates.html.

Text

Wolfram Research (2022), DeleteAdjacentDuplicates, Wolfram Language function, https://reference.wolfram.com/language/ref/DeleteAdjacentDuplicates.html.

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Wolfram Research (2022), DeleteAdjacentDuplicates, Wolfram Language function, https://reference.wolfram.com/language/ref/DeleteAdjacentDuplicates.html.

CMS

Wolfram Language. 2022. "DeleteAdjacentDuplicates." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/DeleteAdjacentDuplicates.html.

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Wolfram Language. 2022. "DeleteAdjacentDuplicates." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/DeleteAdjacentDuplicates.html.

APA

Wolfram Language. (2022). DeleteAdjacentDuplicates. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/DeleteAdjacentDuplicates.html

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Wolfram Language. (2022). DeleteAdjacentDuplicates. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/DeleteAdjacentDuplicates.html

BibTeX

@misc{reference.wolfram_2025_deleteadjacentduplicates, author="Wolfram Research", title="{DeleteAdjacentDuplicates}", year="2022", howpublished="\url{https://reference.wolfram.com/language/ref/DeleteAdjacentDuplicates.html}", note=[Accessed: 25-March-2025 ]}

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@misc{reference.wolfram_2025_deleteadjacentduplicates, author="Wolfram Research", title="{DeleteAdjacentDuplicates}", year="2022", howpublished="\url{https://reference.wolfram.com/language/ref/DeleteAdjacentDuplicates.html}", note=[Accessed: 25-March-2025 ]}

BibLaTeX

@online{reference.wolfram_2025_deleteadjacentduplicates, organization={Wolfram Research}, title={DeleteAdjacentDuplicates}, year={2022}, url={https://reference.wolfram.com/language/ref/DeleteAdjacentDuplicates.html}, note=[Accessed: 25-March-2025 ]}

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@online{reference.wolfram_2025_deleteadjacentduplicates, organization={Wolfram Research}, title={DeleteAdjacentDuplicates}, year={2022}, url={https://reference.wolfram.com/language/ref/DeleteAdjacentDuplicates.html}, note=[Accessed: 25-March-2025 ]}