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MathGroup Archive 2007

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Re: Find index of maximal element in multi-dimensional array

  • To: mathgroup at smc.vnet.net
  • Subject: [mg73533] Re: [mg73492] Find index of maximal element in multi-dimensional array
  • From: Andrzej Kozlowski <akoz at mimuw.edu.pl>
  • Date: Wed, 21 Feb 2007 01:48:19 -0500 (EST)
  • References: <200702201115.GAA07673@smc.vnet.net>



On 20 Feb 2007, at 12:15, Andrew Moylan wrote:

> Hi all,
>
> Here's a two-dimensional array of numbers:
>
> z = Table[Random[], {5}, {6}]
>
> What's an efficient way of finding the index of the maximal element of
> z? Here's one way:
>
> Last[Sort[Flatten[MapIndexed[{#2, #1} & , z, {2}], 1],
>    OrderedQ[{#1[[2]], #2[[2]]}] & ]]
>
> The output is like this:
>
> {{5, 4}, 0.921344}
>
> But it's so untidy. Any better ideas?
>
> Cheers,
>
> Andrew
>
>

If your list contains only numbers you can do this:

z = Table[Random[], {5}, {6}];


Position[z, Max[z]]
{{3, 6}}

and then

Extract[z, %]

{0.9856362205505433}

Andrzej Kozlowski


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