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MathGroup Archive 1996

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Re: VectorToMatrix

  • To: mathgroup at smc.vnet.net
  • Subject: [mg4359] Re: VectorToMatrix
  • From: Count Dracula <lk3a at kelvin.seas.virginia.edu>
  • Date: Thu, 11 Jul 1996 01:02:33 -0400
  • Organization: University of Virginia
  • Sender: owner-wri-mathgroup at wolfram.com

In Message-ID: <4qqn5d$49m at dragonfly.wolfram.com>
Robert Pratt <rpratt at math.unc.edu> wrote:

> I want to define a function VectorToMatrix[list_, n_] that behaves as 
> follows:

> VectorToMatrix[{a,b,c,d,e,f,g,h,i,j}, 4]//MatrixForm

>       0 a b c d
>       0 0 e f g
>       0 0 0 h i
>       0 0 0 0 j

Here's one solution:


vectomat[v_List, n_Integer] := 
  Flatten /@ Transpose[{(Table[0, {#1}] & ) /@ Range[n], (Take[v, #1] & ) /@ 
   FoldList[Plus, {1, n}, Transpose[{Range[n, 2, -1], Range[n - 1, 1, -1]}]]}]


In[3]:= vec = {a, b, c, d, e, f, g, h, i, j, k, l, m, n, p};


In[4]:= MatrixForm[vectomat[vec, 5]]

Out[4]//MatrixForm= 0   a   b   c   d   e

                    0   0   f   g   h   i

                    0   0   0   j   k   l

                    0   0   0   0   m   n

                    0   0   0   0   0   p


-- 
___________________________________________________________________________________
Levent Kitis           lk3a at cars.mech.virginia.edu    lk3a at kelvin.seas.virginia.edu
University of Virginia Department of Mechanical, Aerospace, and Nuclear Engineering  

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