[Rd] embedding R in c++ (Qt) application

[Peter.Peyk at unibas.ch]

Hi Dirk,

I've had a closer look now at Rcpp and I've found a lot
of constructors and functions that take SEXPs as input - so the way back from
R to C++ seems clear to me.

However, I don't know how to pass my data from c++ to R . I've managed
to have the embedded R evaluate commands (construct vectors and do  
something with them) with the help of the official manual,
but I couldn't assign for instance an RcppVector to an SEXP or any of  
these constructed vectors ...
The only clue I had is the dataframe that is constructed in the  
included Rcpp example  - but it's used only with a custom made  
function - not with standard R functions which would be my goal with  
the ANOVA.

Thanks for your help!!!
Peter





>
> Peter,
>
> On 18 June 2008 at 14:13, Peter.Peyk at unibas.ch wrote:
> | Hi R-Developers,
> |
> | I'm working on running statistical analyses with embedded R from a
> | Qt-GUI-application (C++).
> |
> | I've been able to link with R libraries, but I'm having a hard time to
> | understand the C-coding examples. I'm a C++, not a C programmer (never
> | used malloc before), and many of the R-specific
> | functions/keywords/macros (for instance (UN)PROTECT, SETCAR, all the
> | data types (SEXP, CHARSXP etc..) ) don't mean anything to me. The
> | section on the SEXP type in the R-internals doc didn't tell me much.
> | How can I create such objects containing my data? how can I extract
> | numbers or strings from SEXPs?
>
> Have a look at RCpp at http://r-forge.r-project.org. While initially written
> for accessing C++ from R, it works perfectly well the other way too.  Thanks
> to a number of (templated) classes, it abstracts away a lot of the underlying
> C representation.
>
> I also use for embedded R inside of C++.
>
> [...]
>
> | My goal is to prepare some data for R to run an ANOVA on, run it, and
> | retrieve the results to display them on the GUI. Can you suggest me a
> | helpfiles/documentations to read for this?
>
> That should work just fine. One of my apps at work gathers simulation data in
> STL vectors of vectors, passes that to an R matrix via one RCpp invocation. I
> then assign that object to an R object in the embedded R instances, and let R
> run analysis on it.  Much nicer / easier than going the old route of export
> to csv, calling R, reimportting, ....
>
> Hth, Dirk
>
> --
> Three out of two people have difficulties with fractions.
>