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MathGroup Archive 2000

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Re: Getting coordinates of array member

  • To: mathgroup at smc.vnet.net
  • Subject: [mg26292] Re: [mg26247] Getting coordinates of array member
  • From: BobHanlon at aol.com
  • Date: Sun, 10 Dec 2000 00:20:02 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

GetPos[{x_, y_}, mat_List] := mat[[y, x]];

GetCoord[value_, mat_List] := Reverse /@ Position[mat, value];

mat = Partition[Range[9], 3];

GetPos[{1, 3}, mat]

7

GetCoord[%, mat]

{{1, 3}}

This is a list of coordinates since, in general, there can be more than one 
coordinate with the specified value. For example,

mat = IdentityMatrix[3];

GetCoord[1, mat]

{{1, 1}, {2, 2}, {3, 3}}

Bob Hanlon

In a message dated 12/6/00 3:08:08 AM, stephhebert at yourpants~videotron.ca 
writes:

>Ok, let's say I have this
>
>     1  2  3
>    -----------
> 1| 1  2  3
> 2| 4  5  6
> 3| 7  8  9
>
>A 3x3 matrice or array.  Each number in the array represents its' position
>from top left to bottom right.
>
>What I need to do is:
>
>Find what position 1,3 is.  Just by looking at the array, we find that
>7 is
>the answer.
>
>Find what are the coordinates of 7.  Again just by looking at the array
>we
>see that the answer is 1,3
>
>I need to come up with a simplu function that will return these.
>
>pos = GetPos(x,y)
>
>coord = GetCoord(pos)
>


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