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From Kedar Palsule <palsule.ke...@gmail.com>
Subject Re: [math] Re: NormalDistribution
Date Mon, 22 Feb 2010 15:54:40 GMT
Hi Team,

I cant figure out how to download the development version 2.1 of Apache Math
Commons.  Alternatively, it would be good if I could figure out how to
download the nightly build.
The problem is that the official release, version 2.0, has a bug in a part
of the code that I need.

Please let me knowif I can do either
Best Regards,
Kedar

On Mon, Feb 22, 2010 at 5:59 AM, kalpa rajadurai <arkalpa@gmail.com> wrote:

> Hi Team,
>
> Thanks for your quick response.
>
> We would like to know, when this bug will be fixed and probably when
> Commons
> Math 2.1 Version would be released? As our project is dependent on your
> API,
> it would be highly appreciated if we get the fix or any kind of work around
> as soon as possible.
>
> Thanks in advance
>
> On Sat, Feb 20, 2010 at 8:41 PM, Phil Steitz <phil.steitz@gmail.com>
> wrote:
>
> > kalpa rajadurai wrote:
> > > Hi Team,
> > >
> > > We are working on a small project in designing a web based statistical
> > > calculator, supporting certain distribution functions.
> > >
> > > we used  method *cummulativeProbability(double x)* of *class
> > > NormalDistributionImpl* for implementing Normal distribution function.
> > >
> > > We tried to cross check Apache API's result with that of OpenOffice
> Calc
> > and
> > > Excel's result. In most of the cases, the results matched with each
> > other.
> > > But in certain rare cases, the cumulativeProbability() method returned
> by
> > > slightly different result when compared to the result returned by
> > NORMDIST()
> > > function of openoffice calc and Excel.
> > >
> > > Here goes the illustration of the case where we found the mismatch in
> > > results:
> > >
> > > *Using Apache's API:*
> > > NormalDistribution normDist = new NormalDistributionImpl(40,1.5)
> > > ;
> > > try{
> > > System.out.println("cummulative probability::
> > > "+normDist.cumulativeProbability(0.908789));
> > > }
> > > catch(MathException e){
> > > e.printStackTrace();
> > > }
> > >
> > > *Result:*
> > > cummulative probability:: *-8.104628079763643E-15*
> > >
> > > *Using openoffice calc:*
> > > Same input values given in openoffice calc using the formula:
> > > *=NORMDIST(0.908789;40;1.5;1)*
> > >
> > > *Result:*
> > > *0.0*
> > >
> > > *Using Microsoft Excel:*
> > > Same input values given in excel using the formula:
> > > *=NORMDIST(0.908789;40;1.5;1)*
> > >
> > > *Result:*
> > > *5.0738E-150*
> > >
> > > *Different results:*
> > > Apache  -8.104628079763643E-15
> > > Openoffice 0.0
> > > Excel 5.0738E-150
> > >
> > > We wish to know the following things,
> > > 1.) What is the reason for this variation in results?
> >
> > The difference is due to different numeric algorithms used to
> > approximate the cumulative probabilities - in particular how extreme
> > values are handled.  The probability in the example is very close to
> > zero - all three agree on that.
> >
> > > 2.) Which result is more accurate?
> >
> > Excel is likely the best answer; though the only confirmation that I
> > can give of that is that R gives the same answer and the correct
> > answer is certainly positive.  The worst answer is the one reported
> > by commons-math.  The value should not be negative.  This is likely
> > related to an open bug (MATH-301).  Thank you for reporting this.
> >
> > > 3.) Is there any possibility to get the same results as Open Office or
> > Excel
> > > for this case, using Apache's API?
> >
> > Commons Math 2.1 will correct the bug mentioned above, so we will
> > return either 0 or a positive value for this and other extreme tail
> > probabilities.
> >
> > Thanks again for pointing out the discrepancy.
> >
> > Phil
> >
> > >
> > > Hope to receive reply from your team at the earliest as possible.
> > > Thanks in Advance
> > >
> >
> >
> > ---------------------------------------------------------------------
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> > For additional commands, e-mail: user-help@commons.apache.org
> >
> >
>
>
> --
> Karpaga R
>
> "Did you always know that?"
> "No, I didn't. But I believed"
>  ---Matrix III
>

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