PositionLargest

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`PositionLargest`

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PositionLargest[list]

gives the positions of the numerically largest value in list.

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PositionLargest[list,n]

gives the positions of the first n largest values.

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PositionLargest[list,n,orderfun]

gives the positions of the n largest values in list as determined by orderfun.

Details

PositionLargest by default compares values by numerical magnitude, returning the list of positions of the largest value or n largest values.
PositionLargest[list] gives a single list for the largest value.
PositionLargest[list,n] gives a list of n sublists for the n largest values, or as many as are available if fewer than n.
PositionLargest expects all objects to be comparable with one another, based on the ordering function.

Examples

open allclose all

Basic Examples (2)Summary of the most common use cases

Find positions of the largest value in a list:

In[1]:=1

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https://wolfram.com/xid/0c0p21z2jss76-fye26i

Out[1]=1

Get lists of positions for the three largest values:

In[1]:=1

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https://wolfram.com/xid/0c0p21z2jss76-i3l6hj

Out[1]=1

Scope (6)Survey of the scope of standard use cases

Find positions of the two largest values in an association:

In[1]:=1

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https://wolfram.com/xid/0c0p21z2jss76-diccrh

Out[1]=1

PositionLargest works with arbitrary numeric values:

In[1]:=1

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https://wolfram.com/xid/0c0p21z2jss76-3dwb7v

Out[1]=1

PositionLargest can work with orderings of non-numeric data:

In[1]:=1

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https://wolfram.com/xid/0c0p21z2jss76-j9ubu2

Out[1]=1

PositionLargest uses numeric ordering by default:

In[1]:=1

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https://wolfram.com/xid/0c0p21z2jss76-ixmoen

Out[1]=1

Instead use canonical ordering:

In[2]:=2

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https://wolfram.com/xid/0c0p21z2jss76-5skp60

Out[2]=2

PositionLargest works on lists of Quantity expressions:

In[1]:=1

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https://wolfram.com/xid/0c0p21z2jss76-uidkau

Out[1]=1

In[2]:=2

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https://wolfram.com/xid/0c0p21z2jss76-6zv4dw

Out[2]=2

PositionLargest works on lists of DateObject expressions:

In[1]:=1

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https://wolfram.com/xid/0c0p21z2jss76-fdqisq

Out[1]=1

In[2]:=2

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https://wolfram.com/xid/0c0p21z2jss76-ff2ija

Out[2]=2

Properties & Relations (4)Properties of the function, and connections to other functions

Find positions of the largest elements in a random list:

In[20]:=20

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https://wolfram.com/xid/0c0p21z2jss76-r2351n

Out[22]=22

Compare to results using Position and Max:

In[23]:=23

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https://wolfram.com/xid/0c0p21z2jss76-x9scg3

Out[23]=23

PositionLargest gives positions of all the largest elements:

In[1]:=1

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https://wolfram.com/xid/0c0p21z2jss76-9m9r0q

Out[1]=1

TakeLargest will only give as many element positions as are requested:

In[2]:=2

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https://wolfram.com/xid/0c0p21z2jss76-edayxf

Out[2]=2

One must specify the count of maximal elements to get all positions corresponding to the largest element using TakeLargest:

In[3]:=3

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https://wolfram.com/xid/0c0p21z2jss76-y3ptag

Out[3]=3

Find positions of the largest elements in a random list:

In[1]:=1

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https://wolfram.com/xid/0c0p21z2jss76-9cdsjz

Out[1]=1

One can use Ordering once the number of largest elements is known:

In[2]:=2

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https://wolfram.com/xid/0c0p21z2jss76-osokih

Out[2]=2

Find positions of the largest elements in a random list:

In[1]:=1

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https://wolfram.com/xid/0c0p21z2jss76-tiqzrb

Out[1]=1

FindPeaks locates positions of all local maximal values:

In[2]:=2

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https://wolfram.com/xid/0c0p21z2jss76-sfupkf

Out[2]=2

When you remove all peak positions that do not correspond to the global maximum value, you lose positions if there happen to be consecutive peaks:

In[3]:=3

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https://wolfram.com/xid/0c0p21z2jss76-ra7zn7

Out[3]=3

Possible Issues (2)Common pitfalls and unexpected behavior

If fewer than the requested count of largest values are present, PositionLargest will give as many as are present:

In[1]:=1

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https://wolfram.com/xid/0c0p21z2jss76-4cvnvp

Out[1]=1

If the elements are not comparable, PositionLargest will not evaluate:

In[1]:=1

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https://wolfram.com/xid/0c0p21z2jss76-kng5d2

Out[1]=1

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