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MathGroup Archive 1995

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Re: How use the Union function (MMA v.2,2 on PC )?

  • To: mathgroup at christensen.cybernetics.net
  • Subject: [mg975] Re: [mg883] How use the Union function (MMA v.2,2 on PC )?
  • From: Allan Hayes <hay at haystack.demon.co.uk>
  • Date: Thu, 4 May 1995 05:54:33 -0400

>From: Boguslaw Ptaszynski <ptaszyns at uci.agh.edu.pl>
>Subject: [mg883] How use the Union function (MMA v.2,2 on PC )?

>Dear Mathgroup
>
>I have wanted to use the Union function to remove repeated elements
>in the following problem :
>
>Clear[pe, pierw, llk, x, i, imax, k, u, fun];
>pe=100; fun=Tan[x]+(2/pe)*x;
>pierw=Table[FindRoot[fun==0, {x, k}], {k, 3, 10, 0.5}];
>imax=Length[pierw]; u=Flatten[pierw]; llk=Table[N[u[[i,2]],7],  
>{i,1,imax}];
>pierw=Union[llk]
>
>but I was unable to get it. Why ?

The different starting points give slightly different answers.
We need to make Union less discriminating, for example.
(I do not show my evaluation of your code)

In[74]:=
	Union[llk, SameTest -> ((Abs[#1-#2] <10^-10)&)]
Out[74]=
	{3.080069, 6.160591, 9.242001}
	
Allan Hayes
hay at haystack.demon.co.uk





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