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Re: Higher precision in Error function Erf[] needed.

  • To: mathgroup at smc.vnet.net
  • Subject: [mg127176] Re: Higher precision in Error function Erf[] needed.
  • From: "Alexey Popkov" <lehin.p at gmail.com>
  • Date: Thu, 5 Jul 2012 06:12:57 -0400 (EDT)
  • Delivered-to: l-mathgroup@mail-archive0.wolfram.com
  • References: <jsbt4i$6pq$1@smc.vnet.net> <jseeua$i3d$1@smc.vnet.net> <jt0rdo$1ah$1@smc.vnet.net>

I just tried  both variants:

Plot[If[Exp[-x] == 0., 0, -1] + x/900, {x, 0, 1000}, Compiled -> False]

Plot[If[Exp[-x] == 0., 0, -1] + x/900, {x, 0, 1000},
Method -> {Compiled -> False}]

In the first case Compiled is shown in red but it works as it should 
according to the documentation page you referenced. But the second method 
suggested on that documentation page does not work.

P.S. Using Trace, I discovered potentially useful error message of Plot:

On[Plot::accbend]
Plot[If[Exp[-x] == 0., 0, -1] + x/900, {x, 0, 1000}]

(*=> Plot::accbend: Target bending angle of 4.999999999999992` not 
satisfied; current maximal bending angle is 72.68343019044056`. >>*)


"Ray Koopman" <koopman at sfu.ca> wrote: news:jt0rdo$1ah$1 at smc.vnet.net...
> On Jul 2, 2:28 am, "Nasser M. Abbasi" <n... at 12000.org> wrote:
>> On 6/30/2012 4:17 AM, Ray Koopman wrote:
>>
>>> Just alter the precision of its input. First define
>>>
>>>    f[x_,n_] := 8*(10 - Abs[10 - 20000*SetPrecision[x,n]])
>>>
>>> Then
>>>
>>>    Plot[Exp@#*(1-Erf@Sqrt@#)&@f[x,20], {x,0,10^-3}, Compiled->False]
>>>
>>> works fine.
>>
>> fyi;
>>
>> using Mathematica 8, the 'Compiled->False' is shown in RED
>> letters, meaning is not valid option for Plot.
>
> So the advice at
> <http://reference.wolfram.com/mathematica/ref/Compiled.html>
> to use Compiled->False when plotting is "no longer operative"?
> 





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