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Re: weibull plot on weibull scaled paper

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  • Subject: [mg116656] Re: weibull plot on weibull scaled paper
  • From: DrMajorBob <btreat1 at>
  • Date: Wed, 23 Feb 2011 05:22:53 -0500 (EST)

This gave the FindRoot:jsing error on the first try just now... and also  
the third try.

dist = WeibullDistribution[7, 200];
data = RandomVariate[dist, 300];
ProbabilityScalePlot[data, "Weibull"]
QuantilePlot[data, dist]

So the error is not unusual.


On Tue, 22 Feb 2011 03:42:21 -0600, Bill Rowe <readnews at>  

> On 2/21/11 at 4:19 AM, btreat1 at (DrMajorBob) wrote:
>> ProbabilityScalePlot often throws a FindRoot::jsing error with
>> random data, and I wonder why.
> Hmm... I've never seen this error when using ProbabilityScalePlot
>> I'm also trying to see the relationship between these two graphs:
>> dist = WeibullDistribution[7, 200];
>> Quiet@ProbabilityScalePlot[data, "Weibull"]
>> QuantilePlot[data, dist]
> I assume after the second line you posted above there was
> something like
> data = RandomReal[dist, {100}];
> else data is undefined and there would be an error when you use
> either ProbabilityScalePlot or QuantilePlot. But to answer your question:
> For ProbabilityScalePlot, the y-axis is the cumulative
> probability function. In effect, the resulting plot is
> equivalent to something like making a log-log plot of the hazard
> function (HazardFunction[WeibullDistribution[7,200],t]) combined
> with a log-log plot of the empirical hazard function and
> modifying the y-axis to be a probability scale.
> For QuantilePlot you are comparing empirical quantiles with
> quantiles of the given distribution. Basically, this is a
> parametric plot with the y-axis given by
> Quantile[WeibullDistribution[7,200],p] and the x-axis given by
> Quantile[data, p] for p running from approximately 1/n to
> approximately n/(n+1) where n is the number of data points.

DrMajorBob at

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