Re: Getting coordinates of array member

• To: mathgroup at smc.vnet.net
• Subject: [mg26263] Re: Getting coordinates of array member
• From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
• Date: Sun, 10 Dec 2000 00:19:37 -0500 (EST)
• Organization: Universitaet Leipzig
• References: <90krir\$r50@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Hi,

that looks not mich like a Mathematica question ?
You may look at "The Art of Computer Programming" Volume I
that contains an extensive chapter on linear addressing.

You have a (n,m) array and

(i,j)=(1,3)

the linear index is k=j*n+i

The reversion is done by

j=Mod[k,n]
i= k-j*n

Regards
Jens

PS: Is it right that you transpose the index because 7 is on

Stephane Hebert wrote:
>
> Hi folks,
>
> 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
>
> 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)
>
> I've done this before, way long ago and can't find it.
>
> Thanks.
>
> --
> Stephane Hebert
> =========================
> stephhebert at yourpants~videotron.ca