[R] cancelling in fraction

[Peter Ehlers]

Greg has provided a solution. Just to answer the question of
why set_complement() is not doing what you think it should:

You need to change your *vectors* nom and denom to *sets*
with as.set().

  -Peter Ehlers

On 2010-04-23 9:42, Greg Snow wrote:
> Here is a different approach that may work for you, or give you a starting place:
>
>> >  library(MASS)
>> >  fractions(60/(220*6))
> [1] 1/22

>> >  From:r-help-bounces at r-project.org  [mailto:r-help-bounces at r-
>> >  project.org] On Behalf Of capybara!
>> >  Sent: Friday, April 23, 2010 7:49 AM
>> >  To:r-help at r-project.org
>> >  Subject: [R] cancelling in fraction
>> >
>> >
>> >  Dear All,
>> >
>> >  I have a fraction of 60./(220.*6.), which equals 1./22.
>> >  My question is how to cancel the fraction so I actually get 1/22
>> >  (actually I
>> >  just need the factor 22) using R. I tried it with prime factor
>> >  decomposition
>> >  from the package "schoolmath":
>> >
>>> >  >  require("schoolmath")
>> >  Loading required package: schoolmath
>>> >  >  nom<- prime.factor(60)
>>> >  >  nom
>> >  [1] 2 2 3 5
>>> >  >  denom<- prime.factor(220 * 6)
>>> >  >  denom
>> >  [1]  2  2  2  3  5 11
>> >
>> >  So far so good, now I just need to take all elements which are in nom
>> >  out of
>> >  denom (if possible).
>> >  For this I use the package "sets", its function set_complement should
>> >  exactly do that, but:
>> >
>>> >  >  require(sets)
>>> >  >  set_complement(nom, denom)
>> >  {2, 2, 11}
>> >
>> >  It gives me {2,2,11} and 2 * 2 * 11 is 44 and not 22.
>> >  What am I doing wrong? Can anybody help me?
>> >  Is there maybe a more elegant way to cancel a fraction than by prime
>> >  factor
>> >  decomposition?
>> >
>> >  Many thanks in advance,
>> >
>> >  Hannes
>> >
>> >
>> >  --
>> >  View this message in context:http://r.789695.n4.nabble.com/cancelling-
>> >  in-fraction-tp2062218p2062218.html
>> >  Sent from the R help mailing list archive at Nabble.com.
>> >
>> >  ______________________________________________
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>> >  PLEASE do read the posting guidehttp://www.R-project.org/posting-
>> >  guide.html
>> >  and provide commented, minimal, self-contained, reproducible code.
> ______________________________________________
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>
>

-- 
Peter Ehlers
University of Calgary