R help - Oct 2009 - API question (embedding R)

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Hello list,

i want to access R from a Pascal program. Basically i only need to be
able to

* start the engine / the interpreter (and keep it running)
* pass strings to it (R code) that should be parsed and executed
* get floats or vectors of floats into R and assign them to R variables
* read the contents of variables and get them back into my Pascal
program. (I dont need this for all possible data structures, just floats
and maybe vectors of floats would be sufficient)

At the moment i have something running that does exactly this via Python
and the rpy bindings, this works but is horribly complicated to install
because of all the needed dependencies. It works like this: the pascal
program loads the python interpreter (this API is extremely simple, i
can get floats and lists of floats in and out of python variables and
have it compile and execute python code), the pascal program then lets
python import the rpy bindings, put the data into python variables, from
there (by executing python code) move the data into R variables and then
finally execute R code (by executing python code that would call into R
to execute R code contained in a string literal). Getting the results
back goes a similar way.

Now i want to make this more straightforward, i need a way to directly
access the R interpreter just like i can already access the python
interpreter. Using the python interpreter from pascal is a child's play,
you really only need to import a handful of functions from the dll and
nothing else, you just call Py_Initialize() and then you can call
PyRun_SimpleString() as often as you want and thats basically all! No
need to convert the whole C header file to pascal, it all fits more or
less into 5 lines of pascal declarations.

I couldn't find an easy documentation of how i could achieve the same
thing with R: load the dll, import only a few needed functions (which
ones do i actually need?) and how to use them. Is there a minimal
example somewhere? What documents should I read? Maybe i missed
something important?

An example would actually be the most important thing, an example tells
more than thousand words.

Thanks in advance,
Bernd Kreuss
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On 26/10/2009 6:56 PM, Bernd Kreuss wrote:
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> 
> Hello list,
> 
> i want to access R from a Pascal program. Basically i only need to be
> able to
> 
> * start the engine / the interpreter (and keep it running)
> * pass strings to it (R code) that should be parsed and executed
> * get floats or vectors of floats into R and assign them to R variables
> * read the contents of variables and get them back into my Pascal
> program. (I dont need this for all possible data structures, just floats
> and maybe vectors of floats would be sufficient)
> 
> At the moment i have something running that does exactly this via Python
> and the rpy bindings, this works but is horribly complicated to install
> because of all the needed dependencies. It works like this: the pascal
> program loads the python interpreter (this API is extremely simple, i
> can get floats and lists of floats in and out of python variables and
> have it compile and execute python code), the pascal program then lets
> python import the rpy bindings, put the data into python variables, from
> there (by executing python code) move the data into R variables and then
> finally execute R code (by executing python code that would call into R
> to execute R code contained in a string literal). Getting the results
> back goes a similar way.
> 
> Now i want to make this more straightforward, i need a way to directly
> access the R interpreter just like i can already access the python
> interpreter. Using the python interpreter from pascal is a child's
play,
> you really only need to import a handful of functions from the dll and
> nothing else, you just call Py_Initialize() and then you can call
> PyRun_SimpleString() as often as you want and thats basically all! No
> need to convert the whole C header file to pascal, it all fits more or
> less into 5 lines of pascal declarations.
> 
> I couldn't find an easy documentation of how i could achieve the same
> thing with R: load the dll, import only a few needed functions (which
> ones do i actually need?) and how to use them. Is there a minimal
> example somewhere? What documents should I read? Maybe i missed
> something important?
> 
> An example would actually be the most important thing, an example tells
> more than thousand words.
You didn't say what platform you're on, but on Windows, it's
relatively
easy to do with R-(D)COM.  I don't know if there's anything similar on 
other platforms, but the R Extensions manual describes how to write a 
new front-end for R.

Duncan Murdoch
> 
> Thanks in advance,
> Bernd Kreuss
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