Re: Re: Plot, Cursor and Spelling Errors questions
- To: mathgroup at smc.vnet.net
- Subject: [mg14495] Re: [mg14437] Re: [mg14393] Plot, Cursor and Spelling Errors questions
- From: Garrett Tim Sos <gts at mindspring.com>
- Date: Fri, 23 Oct 1998 20:59:14 -0400
- References: <199810210732.DAA14854@smc.vnet.net.>
- Sender: owner-wri-mathgroup at wolfram.com
Define garbage.
Yes it worked on Mac 7100/66 just fine. As n is increased to 15, the
difference (error) you plotted is reduced to something on the order of
10 ^ -16.
On a 7100/66:
$MachineEpsilon gives the smallest machine-precision number which can
be added to 1.0 to give a result that is distinguishable from 1.0.
Attributes[$MachineEpsilon] = {Protected}
$MachineEpsilon = 2.220446049250313*^-16
Sounds about right.
It appears that InterpolatingPolynomial uses machine-precision numbers.
I did not investigate if this can be overridden.
Tim
Ranko Bojanic wrote:
>
> ...
>
> n = 15;
> f[x_] := Exp[x];
> xLst = Table[Cos[((2*k - 1)*Pi)/(2*n)], {k, 1, n}]//Reverse; yLst =
> N[Map[f,xLst], 30];
> fLst = Transpose[{xLst, yLst}];
> p[x_] := InterpolatingPolynomial[fLst, x]; Plot[Evaluate[f[x]-p[x]], {x,
> -1, 1}, PlotPoints -> 50];
>
> (with the last line corrected) and everything worked fine? Which
> computer did you use? How did you configure Plot?
>
> On my computer (Power Macintosh 7500/100, with Mathematica 30.1) this
> program produces garbage.
>
> Regards,
> Ranko
- References:
- Re: Plot, Cursor and Spelling Errors questions
- From: Ranko Bojanic <bojanic@math.ohio-state.edu>
- Re: Plot, Cursor and Spelling Errors questions