Hi Robin,

This works! Also your introduction to using S4 methods is very good!

Thanks!

Feng

On Wed, Feb 11, 2009 at 12:20 PM, Robin Hankin <rksh1@cam.ac.uk> wrote:

> Feng
>
> checkout the Brobdingnag package:
>
>
> > library(Brobdingnag)
> > exp(1000)/(exp(1007)+5)
> [1] NaN
>
> > as.numeric(exp(as.brob(1000))/(exp(as.brob(1007))+5))
> [1] 0.000911882
> >
>
> Feng Li wrote:
>
>> Dear R,
>>
>> I have two questions:
>>
>> 1, Why both R and Matlab give 0*Inf==NaN? To my knowledge, it should be
>> zero
>> mathematically. Am I right?
>>
>> 2, I need to calculate e.g. exp(a)/(exp(b)+c), where both a and b are very
>> large numbers (>>1000, e.g a=1000, b=1007, and c=5). R gives me NaN when I
>> use the following command:
>>
>>
>>
>>> exp(1000)/(exp(1007)+5)
>>>
>>>
>> [1] NaN
>>
>> I am pretty sure this should be close to zero. My question is whether
>> there
>> is a general way to solve this kind of question or should I do some
>> settings
>> before computing?
>>
>>
>> Thanks in advance!
>>
>>
>> Feng
>>
>>
>>
>>
>>
>
>
> --
> Robin K. S. Hankin
> Uncertainty Analyst
> University of Cambridge
> 19 Silver Street
> Cambridge CB3 9EP
> 01223-764877
>
>


-- 
Feng Li
Department of Statistics
Stockholm University
106 91 Stockholm, Sweden

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