       Re: Following position change in different vectors

• To: mathgroup at smc.vnet.net
• Subject: [mg117521] Re: Following position change in different vectors
• From: Peter Pein <petsie at dordos.net>
• Date: Mon, 21 Mar 2011 06:17:33 -0500 (EST)
• References: <im4iqj\$d1b\$1@smc.vnet.net>

```Am 20.03.2011 10:53, schrieb Lengyel Tamas:
> Dear Mathworld Users,
>
> Sorry for asking your help again, I hope I'm not spamming too much.
> My problem is the following:
>
> 1) I have 2 vectors with equal length. The positions of the first vector
> correspond to the second vector. So the first element of v2 is calculated
> from the first element of v1, etc.
>
> 2) I wish to sort the first vector in ascending magnitude using Sort[v1].
> Naturally the positions of v1's elements change.
>
> What I want is the same change of position in v2's positions.
>
> (So e.g. if v1's sixth element moves after Sort to  the first position,
> I'd like v2's same position element to follow suit)
>
>
> Tamas
>

Hi Tamas,

use Ordering before sorting v1:
In:= v1 = RandomSample[Range];
v2 = v1^2
Out= {1, 9, 4, 16, 25}

get v2 in the order of sorted v1:
In:= v2s = v2[[Ordering[v1]]]
Out= {1, 4, 9, 16, 25}

In:= v1s = Sort@v1
Out= {1, 2, 3, 4, 5}

Peter

```

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