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Re: Maximum in a list

  • To: mathgroup at smc.vnet.net
  • Subject: [mg97261] Re: [mg97209] Maximum in a list
  • From: Adriano Pascoletti <adriano.pascoletti at dimi.uniud.it>
  • Date: Mon, 9 Mar 2009 01:07:28 -0500 (EST)
  • References: <200903081050.FAA21521@smc.vnet.net>

The problem can be solved in several ways; three of them follow.

Solution 1: based on Ordering and Part
Find the position of a maximizer

In[1]:= mylist = {{1, 2}, {3, 4}, {8, 3}}; Ordering[mylist, -1,
    Last[#1] <= Last[#2] & ]
Out[1]= {2}


then get its value

In[2]:= mylist = {{1, 2}, {3, 4}, {8, 3}}; (mylist[[#1]] & )[
    Ordering[mylist, -1, Last[#1] <= Last[#2] & ][[1]]]
Out[2]= {3, 4}


Solution 2: based on Sort[list, crit]

In[3]:= Sort[mylist, Last[#1] <= Last[#2] &][[-1]]
Out[3]= {3, 4}


Solution 3: optimal (linear-time)


In[5]:= Fold[If[Last[#1] < Last[#2], #2, #1] & , First[mylist],
Rest[mylist]]
Out[5]= {3, 4}


Adriano Pascoletti


2009/3/8 pacotomi <pacotomi at orange.fr>

> Hi,
>  Suppose a list
>
> mylist={{1,2},{3,4},{8,3}}
>
> I would like to extract the element {i,j} of mylist for which j is max
> (here, it is the second one {3,4}).
>
> Somebody could help me, please?
>
> Pacotomi
>


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