
Re: VectorToMatrix
Posted:
Jul 8, 1996 1:54 AM


In article <4qqn5d$49m@dragonfly.wolfram.com>, Robert Pratt <rpratt@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 > >Now n can be determined from Length[list], which will always be equal to >n choose 2 for some n. But I would rather input n to save that >computation. (I will be doing this for a lot of vectors.) > >Any ideas? > >Rob Pratt >Department of Mathematics >The University of North Carolina at Chapel Hill >CB# 3250, 331 Phillips Hall >Chapel Hill, NC 275993250 > >rpratt@math.unc.edu
Another possible solution to this uses the MatrixManipulation standard package:
<<LinearAlgebra`MatrixManipulation` utmatrix[ x_List, n_Integer ] := Module[ { a, b, c }, a = Drop[ UpperDiagonalMatrix[ b, n + 1 ], 1 ]; c = DeleteCases[ Flatten[ a ], 0 ]; a /. Thread[ Rule[ c, x ] ] ] /; Positive[ n ] && (Length[ x ] == n(n + 1)/2) utmatrix[ {a,b,c,d,e,f,g,h,i,j}, 4 ] // MatrixForm
Paul
************************************************************************** * Paul A. Rubin Phone: (517) 4323509 * * Department of Management Fax: (517) 4321111 * * Eli Broad Graduate School of Management Net: RUBIN@MSU.EDU * * Michigan State University * * East Lansing, MI 488241122 (USA) * ************************************************************************** Mathematicians are like Frenchmen: whenever you say something to them, they translate it into their own language, and at once it is something entirely different. J. W. v. GOETHE

