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MathGroup Archive 1998

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Box manipulation

  • To: mathgroup at smc.vnet.net
  • Subject: [mg13514] Box manipulation
  • From: Silvia Heubach <silvi at nospam.cinenet.net>
  • Date: Fri, 31 Jul 1998 04:33:28 -0400
  • Sender: owner-wri-mathgroup at wolfram.com

	I have ventured into the deep parts of the internal Mathematica
	representations (at least for me). What I am trying to do is to
	compute a general solution to a system of difference equations
	in terms of the eigenvectors and eigenvalues. I have computed
	these terms and would now like to output them in nice
	mathematical form. I thought I had the solution until I came
	across some eigenvalues that were square roots and eigenvectors
	that were complex and resulted in sine and cosine terms. Below
	is my partial solution. The lists A and B are just as an
	example, but they reflect the structures I am dealing with. My
	code works for lists A and B, and the output gives you the
	format I would like to achieve. Lists A1 and B1 contain
	elements for which the code does not work. I tried
	unsucessfully commands like ToString or ToBoxes, but either its
	not the right thing or I used it at the wrong place.

	Any help is appreciated. Please email me directly at
	silvi at cinenet.net, as I have unsubscribed for summer from the
	list. Thanks in Advance
	
	Silvia Heubach
	
	
	**** This one works ***************************************
	
	A={1,2,3,4};   (*to stand for eigenvalues *)
	B={{1,2},{-3,2},{-1,0},{3,4}}  ;     (* to stand for eigenvectors*)
	
	
	Clear[str];
	str={"x(k)="};
	solterms=Table[{SubscriptBox["c",ToString[i]],"*",SuperscriptBox[A[[i]],"k"],
	      "*","(",GridBox[Partition[B[[i]],1]],")","+"},{i,1,4}];
	newstr=Drop[Flatten[AppendTo[str,solterms]],-1];
	foo=RowBox[newstr]//DisplayForm;
	Print[foo]
	
	**** Here is where it breaks down - just different input, no change in
code
	(except ajusting the names of the lists **************************
	
	A1={1,Sqrt[2],3,4}; B1={{1,2},{Cos[2 k],0},{1,1},{Sin[-2 k],1}};
	
	Clear[str];
	str={"x(k)="};
	solterms=Table[{SubscriptBox["c",ToString[i]],"*",SuperscriptBox[A1[[i]],"k"],
	      "*","(",GridBox[Partition[B1[[i]],1]],")","+"},{i,1,4}];
	newstr=Drop[Flatten[AppendTo[str,solterms]],-1];
	foo=RowBox[newstr]//DisplayForm;
	Print[foo]
	
	
	**********


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