[R] Exponentiate very large numbers

[Rui Barradas]

Sorry, it should be:

Divide both terms by exp(log(0.1) + log.b) to give

tmp1 <- exp(log.a - log(0.1) - log.b) - 1
result <- tmp1 * exp(log(0.1) + log.b)


Rui Barradas

Em 04-02-2013 18:53, Rui Barradas escreveu:
> Hello,
>
> Use a simple transfomation. Divide both t
>
> log.a <- 1347
> log.b <- 1351
> tmp1 <- exp(log.a - log(0.1) - log.b) - 1
> result <- tmp1 * exp(0.1 + log.b)  # -Inf
>
> Using base 10, the result would be
>
> -4.405386507*10^585
>
> a number too large for R. See the help page ?.Machine
>
>
> Hope this helps,
>
> Rui Barradas
>
>
> Em 04-02-2013 15:11, francesca casalino escreveu:
>> Dear R experts,
>>
>> I have the logarithms of 2 values:
>>
>> log(a) = 1347
>> log(b) = 1351
>>
>> And I am trying to solve this expression:
>>
>> exp( ln(a) ) - exp( ln(0.1) + ln(b) )
>>
>> But of course every time I try to exponentiate the log(a) or log(b)
>> values I get Inf. Are there any tricks I can use to get a real result
>> for exp( ln(a) ) - exp( ln(0.1) + ln(b) ), either in logarithm or
>> exponential form?
>>
>>
>> Thank you very much for the help
>>
>> ______________________________________________
>> R-help at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.