Re: Gaps in plotted graph, probably resulting from real values being miscomputed as complex
- To: mathgroup at smc.vnet.net
- Subject: [mg123492] Re: Gaps in plotted graph, probably resulting from real values being miscomputed as complex
- From: Andy Ross <andyr at wolfram.com>
- Date: Fri, 9 Dec 2011 05:54:23 -0500 (EST)
- Delivered-to: l-mathgroup@mail-archive0.wolfram.com
On 12/8/2011 4:22 AM, jdm wrote:
> Plot[Log[2,
> PDF[NormalDistribution[0, 1],
> InverseCDF[NormalDistribution[0, 1], (1 - 2^(-x))]]^2], {x, 1,
> 256}, PlotRange -> {-500, 0}]
>
> plots up to about x=56, and then nothing.
>
> Based on similar behaviour under another system, I suspect that some sort of
> calculation error as 1 - 2^(-x) approaches 1 is causing some of the
> values that should be plotted to be wrongly computed as complex
> numbers, but have no way of confirming this and don't understand why
> the real-valued values aren't being plotted for their corresponding x
> if this is the case.
>
> Can anyone suggest anything?
>
> Thanks,
>
> James McLaughlin.
>
Try boosting the working precision of plot.
Plot[Log[2,
PDF[NormalDistribution[0, 1],
InverseCDF[NormalDistribution[0, 1], (1 - 2^(-x))]]^2], {x, 1,
256}, PlotRange -> {-500, 0}, WorkingPrecision -> 20]
-Andy