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MathGroup Archive 2006

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Re: Initialize a matrix in mathematica

  • To: mathgroup at smc.vnet.net
  • Subject: [mg66758] Re: [mg66742] Initialize a matrix in mathematica
  • From: Murray Eisenberg <murray at math.umass.edu>
  • Date: Mon, 29 May 2006 06:05:46 -0400 (EDT)
  • Organization: Mathematics & Statistics, Univ. of Mass./Amherst
  • References: <200605281008.GAA10210@smc.vnet.net>
  • Reply-to: murray at math.umass.edu
  • Sender: owner-wri-mathgroup at wolfram.com

All you need is:

   a = Table[i^2, {1}, {i, 5}]
{{1, 4, 9, 16, 25}}

Avoid all Do, For, and other explicit loops where you can in an 
interpreted language such as Mathematica.  (Let the underlying system 
code take care of creating the loops actually needed.)

ashesh wrote:
> Hi All,
> 
> Have programmed in another system until now and am trying to shift to
> Mathematica and facing some diffciulties
> 
> I would like to create a matrix, say a[ndiv] and would like to
> initilize all the value to i^2 (or any other value). The size of the
> matrix is not fixed.
> 
> The code I tried to use is:
> 
> ndiv = 5;
> a = {};
> For[i=1, i<=ndiv, i++,
> a[[i]] = i*i;
> ];
> a
> 
> This is producing the following error:
> partw: Part 1 of {} does not exist and so on.
> 
> I understand that I am not creating a matrix of size 1*ndiv for the
> data to be fed it.
> 
> So I tried using Table as follows:
> 
> a = Table[0,{1},{ndiv}] followed by the above For loop (when I wanted
> to initialize the matrix with say i*i;
> 
> Hope some one can help me in doing the above operation
> 
> Regs.
> 
> 

-- 
Murray Eisenberg                     murray at math.umass.edu
Mathematics & Statistics Dept.
Lederle Graduate Research Tower      phone 413 549-1020 (H)
University of Massachusetts                413 545-2859 (W)
710 North Pleasant Street            fax   413 545-1801
Amherst, MA 01003-9305


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