R help - Sep 2007 - Number -> Fraction

Hi everybody!
I'm new to this list and also to the R program.

I'd like to know if there is a function able to convert results into 
Fractional form like my scientific calculator have. For example:
> 1/3
[1] 0.3333333
> function_that_return_a_fraction_from_numbers(0.3333333)
[1] 1/3

Thanks

Mauro

-- 


Man, he is constantly growing 
and when he is bound by a set 
pattern of ideas or way
of doing things, that's when
he stops growing
	-- Bruce Lee

Mauro Arnoldi wrote:
> Hi everybody!
> I'm new to this list and also to the R program.
> 
> I'd like to know if there is a function able to convert results into 
> Fractional form like my scientific calculator have. For example:
> 
>> 1/3
> [1] 0.3333333
> 
>> function_that_return_a_fraction_from_numbers(0.3333333)
> [1] 1/3

0.333333 is not equal 1/3, hence it is impossible to do that in a 
reliable manner.

Uwe Ligges

> Thanks
> 
> Mauro
>

Welcome (benvenuto),


see "fractions" in library MASS

es:
> fractions(1/2)
[1] 1/2

Ciao

Stefano



On Thu, Sep 13, 2007 at 04:54:01PM +0200, Mauro Arnoldi wrote:
<Mauro>Hi everybody!
<Mauro>I'm new to this list and also to the R program.
<Mauro>
<Mauro>I'd like to know if there is a function able to convert results
into
<Mauro>Fractional form like my scientific calculator have. For example:
<Mauro>
<Mauro>> 1/3
<Mauro>[1] 0.3333333
<Mauro>
<Mauro>> function_that_return_a_fraction_from_numbers(0.3333333)
<Mauro>[1] 1/3
<Mauro>
<Mauro>Thanks
<Mauro>
<Mauro>Mauro
<Mauro>
<Mauro>-- 
<Mauro>
<Mauro>
<Mauro>Man, he is constantly growing 
<Mauro>and when he is bound by a set 
<Mauro>pattern of ideas or way
<Mauro>of doing things, that's when
<Mauro>he stops growing
<Mauro>	-- Bruce Lee
<Mauro>
<Mauro>______________________________________________
<Mauro>R-help a r-project.org mailing list
<Mauro>https://stat.ethz.ch/mailman/listinfo/r-help
<Mauro>PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
<Mauro>and provide commented, minimal, self-contained, reproducible code.

Try:

library(MASS)
?fractions


On 9/13/07, Mauro Arnoldi <agharti81 at tiscali.it>
wrote:
> Hi everybody!
> I'm new to this list and also to the R program.
>
> I'd like to know if there is a function able to convert results into
> Fractional form like my scientific calculator have. For example:
>
> > 1/3
> [1] 0.3333333
>
> > function_that_return_a_fraction_from_numbers(0.3333333)
> [1] 1/3
>
> Thanks
>
> Mauro
>
> --
>
>
> Man, he is constantly growing
> and when he is bound by a set
> pattern of ideas or way
> of doing things, that's when
> he stops growing
>        -- Bruce Lee
>
> ______________________________________________
> 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.
>

look at ?fractions
> fractions(.33333)
[1] 1/3

On Thu, 13 Sep 2007, Mauro Arnoldi wrote:
> Hi everybody!
> I'm new to this list and also to the R program.
>
> I'd like to know if there is a function able to convert results into
> Fractional form like my scientific calculator have. For example:
>
> > 1/3
> [1] 0.3333333
>
> > function_that_return_a_fraction_from_numbers(0.3333333)
> [1] 1/3
>
> Thanks
>
> Mauro
>
> --
>
>
> Man, he is constantly growing
> and when he is bound by a set
> pattern of ideas or way
> of doing things, that's when
> he stops growing
> 	-- Bruce Lee
>
> ______________________________________________
> 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.
>

Alle gioved? 13 settembre 2007, Stefano Calza ha scritto:
>
> see "fractions" in library MASS
>
Yeah!
> 1/3
[1] 0.3333333
> fractions(0.3333333)
[1] 1/3

Great! Thanks! (grazie :) )

Mauro

On Thu, 13 Sep 2007, Mauro Arnoldi wrote:
> Hi everybody!
> I'm new to this list and also to the R program.
>
> I'd like to know if there is a function able to convert results into
> Fractional form like my scientific calculator have. For example:
>
>> 1/3
> [1] 0.3333333
>
>> function_that_return_a_fraction_from_numbers(0.3333333)
> [1] 1/3
>
This must have some restrictions (so it doesn't return 3333333/1000000, 
which would be a more accurate fraction).

One approach is
> unfrac <- function(x, max=100, tol=0.01){
     num <- x * (1:max)
     err <- (num - round(num)) * (1:max)
     if (!any(abs(err) < tol))
         return(NA)
     i <- which.min(abs(err))
     c(round(num[i]), i)
}

This returns the best fraction approximation with denominator up to `max`, 
where `best` is in terms of the non-integer part of the numerator, and no 
answer is given if the non-integer part of the numerator is more than 
`tol`
> unfrac(0.3333333)
[1] 1 3
> unfrac(pi)
[1] NA
> unfrac(pi,max=1000)
[1] 355 113
> unfrac(pi,tol=0.1)
[1] 22  7

 	-thomas