in reply to Very small numbers

I think we need nore detail on your problem to give a useful answer. What numbers are causing this problem? What distribution function are you trying to evaluate? Do you mean fdistr? Show us your code.

If your numbers are so small that they are causing arithmetic underflow of your floating point represenentation, then you need to be more clever in how you deal with them. A general technique is to work with the log of a very small number, rather than the number itself. Then multiplications become additions, etc.

Another approach is derive a perturbative expansion of your probabilitiy distribution for very small numbers and use that directly.

-Mark

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Re: Re: Very small numbers
by Win (Novice) on Feb 10, 2004 at 10:36 UTC
    I think that I will have to do something along the lines of: 

    
 if ($numerator > 7169 || $denominator > 1650){
          print "Do nothing";
          # Place another method in here
        }
        else {     
          my $fprob = Statistics::Distributions::fprob($numerator,$den
+ominator,0.025);
}

    [download]

    The FINV function in Excel (equivalent to the fprob function in Statistics::Distributions) is able to go above the denominator and numerator values specified as limits here.

[reply]
[d/l]
      Sorry, please replace fprob with fdistr in my previous post.
[reply]

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