[R] system solver in R

[peter dalgaard]

Once you figure out how to decipher the output, you realise that it actually does give you all 4 roots, including the two real ones:

...
> a <- .Last.value
> complex_cartesian <- function(x,y) x+(0+1i)*y
> eval(a$text[[1]][[2]][[3]])
[1] -1.00028+0.988174i
> eval(a$text[[1]][[3]][[3]])
[1] -1.00028-0.988174i
> eval(a$text[[1]][[4]][[3]])
[1] 0.03634399
> eval(a$text[[1]][[5]][[3]])
[1] -1.988165

(No, I don't quite know what I am doing either...)

-pd


> On 20 Nov 2018, at 13:09 , Engin Yılmaz <ispanyolcom using gmail.com> wrote:
> 
> Dea(R)
> I try to solve one equation but this program did not give me real roots
> for example
> yacas("Solve( 5/((1+x)^1) + 5/((1+x)^2) + 5/((1+x)^3) + 105/((1+x)^4) -105
> ==0, x)")
> gave me following results
> How can I find real roots?
> 
> expression(list(x == complex_cartesian((1/42 - ((1/63 -
> ((root(7339451281/3087580356,
>    2) - 4535/71442)^(1/3) - (4535/71442 + root(7339451281/3087580356,
>    2))^(1/3)))/21 - -2/21)/(4 * root(((root(7339451281/3087580356,
>    2) - 4535/71442)^(1/3) - (4535/71442 + root(7339451281/3087580356,
>    2))^(1/3) - 1/63)^2/4 + 1, 2)))/2 - 1, root(4 *
> (((root(7339451281/3087580356,
>    2) - 4535/71442)^(1/3) - (4535/71442 + root(7339451281/3087580356,
>    2))^(1/3) - 1/63)/2 + root(((root(7339451281/3087580356,
>    2) - 4535/71442)^(1/3) - (4535/71442 + root(7339451281/3087580356,
>    2))^(1/3) - 1/63)^2/4 + 1, 2)) - (((1/63 -
> ((root(7339451281/3087580356,
>    2) - 4535/71442)^(1/3) - (4535/71442 + root(7339451281/3087580356,
>    2))^(1/3)))/21 - -2/21)/(4 * root(((root(7339451281/3087580356,
>    2) - 4535/71442)^(1/3) - (4535/71442 + root(7339451281/3087580356,
>    2))^(1/3) - 1/63)^2/4 + 1, 2)) - 1/42)^2, 2)/2),...more
> 
> 
> 
> 
> Engin Yılmaz <ispanyolcom using gmail.com>, 20 Kas 2018 Sal, 12:53 tarihinde şunu
> yazdı:
> 
>> Thanks a lot!
>> 
>> Berend Hasselman <bhh using xs4all.nl>, 20 Kas 2018 Sal, 12:02 tarihinde şunu
>> yazdı:
>> 
>>> 
>>> 
>>> R package Ryacas may be what you want.
>>> 
>>> Berend
>>> 
>>> 
>>>> On 20 Nov 2018, at 09:42, Engin Yılmaz <ispanyolcom using gmail.com> wrote:
>>>> 
>>>> Dea(R)
>>>> 
>>>> Do you know any system solver in R ?
>>>> 
>>>> For example, in matlab, is very easy
>>>> 
>>>> syms a b c x eqn = a*x^2 + b*x + c == 0; sol = solve(eqn)
>>>> 
>>>> How can I  find this type code in R (or directly solver)?
>>>> 
>>>> *Since(R)ely*
>>>> Engin YILMAZ
>>>> 
>>>>      [[alternative HTML version deleted]]
>>>> 
>>>> ______________________________________________
>>>> R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
>>>> 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.
>>> 
>>> 
>> 
>> --
>> *Saygılarımla*
>> Engin YILMAZ
>> 
> 
> 
> -- 
> *Saygılarımla*
> Engin YILMAZ
> 
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
> R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
> 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.

-- 
Peter Dalgaard, Professor,
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
Office: A 4.23
Email: pd.mes using cbs.dk  Priv: PDalgd using gmail.com