[R] Treating variables as symbols
Gabor Grothendieck
ggrothendieck at gmail.com
Thu Oct 1 17:15:36 CEST 2009
Read the troubleshooting section on the home page: http://ryacas.googlecode.com
Note, in particular, that it currently only works with an older
version of the XML package.
> library(Ryacas)
> packageDescription("XML")$Version
[1] "1.96-0"
> x <- Sym("x")
> Integrate(x*x, x)
[1] "Starting Yacas!"
expression(x^3/3)
On Thu, Oct 1, 2009 at 11:08 AM, ZeMajik <zemajik at gmail.com> wrote:
> Thanks guys, Ryacas is pretty much what I'm looking for!However, I can't
> seem to get it to work properly.
>
> For example:
>
>> yacas("Integrate(x) x")
> Error in parse(text = text, srcfile = NULL) :
> unexpected numeric constant in ""/" ("^" (x ,2 2"
>
> Same thing with expressions such as yacas("x*x")
>
> However
>
>> yacas("2*2")
> expression(4)
>
> So it seems there is a successful connection between yacas and R.
> I didn't find any info on the problem by googling it unfortunately! Any
> ideas what it might be?
>
> Thanks again,
> M
>
> On Thu, Oct 1, 2009 at 3:50 PM, Jorge Ivan Velez
> <jorgeivanvelez at gmail.com>wrote:
>
>> Hi Zemajik,
>> Try this:
>>
>> > y <- function(a) paste(a, '*x', sep="")
>> > y(2)
>> [1] "2*x"
>>
>> Also, take a look at the Ryacas package.
>>
>> HTH,
>> Jorge
>>
>>
>> On Thu, Oct 1, 2009 at 9:46 AM, ZeMajik <> wrote:
>>
>>> Hey,
>>> I'm trying to find how to perform operations with a variable treated as a
>>> symbol.
>>> For, an extremely simple, example I want to integrate a*x with respect to
>>> x
>>> and I want to find the indefinite integral of this, (a*x^2/2), or the
>>> definite integral with some interval for x.
>>>
>>> Another example of such a use would be to create a function
>>> y<-function(x) {a*x}
>>> and by typig y(2) I would get the result 2*a
>>>
>>> Is there a way to treat variables as merely "symbols"?
>>> Any help much appreciated
>>>
>>> -M
>>>
>>> [[alternative HTML version deleted]]
>>>
>>> ______________________________________________
>>> 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.
>>>
>>
>>
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
> 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.
>
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