Re: weibull plot on weibull scaled paper

*To*: mathgroup at smc.vnet.net*Subject*: [mg116656] Re: weibull plot on weibull scaled paper*From*: DrMajorBob <btreat1 at austin.rr.com>*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. Bobby On Tue, 22 Feb 2011 03:42:21 -0600, Bill Rowe <readnews at sbcglobal.net> wrote: > On 2/21/11 at 4:19 AM, btreat1 at austin.rr.com (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 yahoo.com