[Rcpp-devel] how to use functions from other packages

[Siddhartha Chib]

Thanks Dirk.  I was hoping for an example of the use of R functions in 
Rcpp and did take a look at your Journal of Statistical software paper 
but was hoping for more than is there on this issue.
Maybe someone can post a full example.

On a different issue, I tried the inline example in your JSS paper on my 
Windows 7 machine after loading the inline library

src = '
Rcpp::NumericVector xa(a);
Rcpp::NumericVector xb(b);
int n_xa = xa.size(), n_xb = xb.size();

Rcpp::NumericVector xab(n_xa + n_xb - 1);
for (int i = 0; i < n_xa; i++)
for (int j = 0; j < n_xb; j++)
xab[i + j] += xa[i] * xb[j];
return xab;
  '
fun <- cxxfunction(signature(a = "numeric", b = "numeric"),
  src, plugin = "Rcpp")

  R> fun(1:3, 1:4)

and got the following error message

Error in system(cmd, intern = !verbose) : 'C:/Program' not found

What could the problem be?

Thanks in advance on both scores.

Siddhartha.

On 4/23/2011 9:25 PM, Dirk Eddelbuettel wrote:
> On 23 April 2011 at 21:05, Dirk Eddelbuettel wrote:
> |
> | On 23 April 2011 at 20:36, Siddhartha Chib wrote:
> | | This is likely to be too simple a question perhaps.  How does one use specific
> | | functions from other packages when working with Rcpp?  For that matter, is it
> | | possible to use R functions such as optim in Rcpp?
> |
> | Yes, sure. I don't think we have a great example though.
> [...]
> | A concise example would be good.  Maybe another list member has something?
>
> PS This may be obvious too, but let's just state it plainly to be sure: in
>     iterative optimisation, if you repeatedly go back between R and C++ you
>     are likely to give up a bunch of the speed gain Rcpp can otherwise offer.
>     There are other tricks one can use to access the _C_ part of certain R
>     functions.  Frequent list contributor Davor had done some nice work getting
>     at the inner (C language) part of loess(); that is now also in a CRAN
>     package 'rgam' which uses Rcpp and RcppArmdillo:
>
>        http://cran.r-project.org/web/packages/rgam/index.html
>
> Hope this helps,  Dirk
>
>    

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