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MathGroup Archive 2004

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Re: partition of 2D arrray

  • To: mathgroup at smc.vnet.net
  • Subject: [mg49161] Re: partition of 2D arrray
  • From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
  • Date: Tue, 6 Jul 2004 03:33:18 -0400 (EDT)
  • Organization: Universitaet Leipzig
  • References: <ccb54i$ei1$1@smc.vnet.net>
  • Reply-to: kuska at informatik.uni-leipzig.de
  • Sender: owner-wri-mathgroup at wolfram.com

Hi,

lst = {{1, 2, 3, 4}, {5, 6, 7, 8}, {9, 10, 11, 12}, {13, 14, 15, 16}};

lst[[All, {1, 2}]]

Take[#, 2] & /@ lst

Drop[#,-2] & /@ lst

Transpose[Take[Transpose[lst], 2]]

SetAttributes[If, SequenceHold]
MapIndexed[If[Last[#2] <= 2, #1, Sequence[]] &, lst, {2}]

Regards
  Jens

"Ravinder Kumar B." wrote:
> 
> Dear Friends,
> I have a list of 2D data of the following form:
> {{1,2,3,4},{5,6,7,8},{9,10,11,12},{13,14,15,16}};
> In MatrixForm it is 4x4 matrix.
> How do I extract the fisrt two column of the data from the above matrix.
> i.e.,
> {{1,2},{5,6},{9,10},{13,14}}
> 
> --
>  Regards,                                   Jul 2
>     Ravi
> 
>          |~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~|
>          |           Ravinder Kumar Banyal (SRF),                |
>          |          Indian Institute of Astrophysics,            |
>          |           Koramangala Bangalore - 560 034. INDIA      |
>          | email : banyal at iiap.res.in, ravi at crest.ernet.in       |
>          | Ph No : 080 25530672 (IIA)       080 7931972 (Hoskote)|
>          |                                     7931952           |
>           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> Philosophers have interpreted the world in various ways, but the point is
> to change it. --Karl Marx




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