[R] general inverse solver?

[Gabor Grothendieck]

Yacas was completely rewritten in java (Ryacas interfaces to the
C version) since the Ryacas project started so I would not exactly
characterize yacas as dead.   The work that is going on in yacas
may not have high visibility but that does not mean there is none.

Also while Maxima is more sophisticated in terms of algorithms,
yacas is actually more sophisticated from the viewpoint of its
language  which borrows ideas from both imperative and prolog programming
and its interfaces are more sophisticated (it is one of the few CAS systems
that developed an OpenMath interface) and its socket server is
used by the Ryacas interface.  yacas can also translate math expressions
to TeX and do exact arithmetic.

Also to put this in the correct context, yacas does seem capable of
answering the majority of questions that are posed on r-help that need
a CAS in the answer. From a practical viewpoint it does seem to have
the facilities that are most often needed.   The Ryacas vignette has
a survey of some of its algebra capabilities.

That being said, without taking away from yacas there is work going on to
interface R to a second CAS.

On Tue, Feb 10, 2009 at 2:33 AM, Hans W. Borchers
<hwborchers at googlemail.com> wrote:
>
> I know that Ryacas is promoted here whenever requests about symbolic algebra
> or calculus appear on the R-help list. But to say the truth, Yacas itself is
> a very very limited Computer Algebra System and looking onto its home page
> it appears the development will stop or has stopped anyway.
>
> It would be fair to clearly state that there is no R package to solve
> somewhat more involved symbolic mathematical problems. One could then point
> the requestor to one of the open source Computer Algebra Systems  (CAS) such
> as Maxima or Axiom.
>
> Interestingly, the free Math Toolbox Euler by Grossmann has integrated
> Maxima into its numerical environment in a way that is really useful for
> numerical and symbolic computations. I could imagine that in a similar way
> Maxima can be integrated into R bringing the full power of computer algebra
> to the R community.
>
> Hans W. Borchers
> ABB Corporate Research
>
> ----
> Postscript
>
> "The Euler Mathematical Toolbox is a powerful, versatile, and open source
> software for numerical and symbolic computations ... Euler supports symbolic
> mathematics using the open algebra system Maxima."
>
> <http://mathsrv.ku-eichstaett.de/MGF/homes/grothmann/euler/>
>
>
>
> Gabor Grothendieck wrote:
>>
>> The forms of equations are limited but its not limited to just one:
>>
>>> library(Ryacas)
>> Loading required package: XML
>>> x <- Sym("x")
>>> y <- Sym("y")
>>> Solve(List(x+y == 2, x-y == 0), List(x, y))
>> [1] "Starting Yacas!"
>> expression(list(list(x == 2 - y, y == 1)))
>>
>>
>> On Mon, Feb 9, 2009 at 7:45 PM, Carl Witthoft <carl at witthoft.com> wrote:
>>> Gabor G a ecrit:
>>> Check out the Ryacas package.   There is a vignette with some
>>> examples.
>>>
>>> ----
>>> Which led me to the manuals for yacas itself.  I'm guessing there may be
>>> a
>>> way to use yacas'  "AND" construct to combine a few equations and then
>>> hope
>>> the Newton Solver can work with that, but it's not clear that will work.
>>>
>>> TK!Solver is nice because you aren't limited to linear equations, nor to
>>> equations which "fit" into a matrix structure, and because it's legal to
>>> have more than one unknown to be back-solved (assuming the problem is not
>>> under- or over-defined, of course).
>>>
>>> ______________________________________________
>>> 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.
>>>
>>
>
> --
> View this message in context: http://www.nabble.com/general-inverse-solver--tp21902788p21928972.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
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> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>