[Rd] R and C pointers
Adrian Duşa
dusa.adrian at gmail.com
Tue Jun 19 17:40:31 CEST 2012
Dear R devel,
Apologies for these (most probably trivial) questions, doing my first
attempt to call C from R (and actually learning C in the process).
I need to pass a matrix to C, and after reading R-exts.pdf (many
times), I was unable to find how to handle matrices at C-level...
except for, what probably is the answer, that matrices are in fact
vectors with dimensions.
This is a sample code I am using at C level:
±±±±±±±±±±±±±±±±±±±±±±±±
# include <R.h>
# include <Rinternals.h>
# include <R_ext/Rdynload.h>
SEXP foo(SEXP x) {
SEXP dimx;
double *px, *pdimx;
PROTECT(dimx = getAttrib(x, R_DimSymbol));
px = REAL(x);
UNPROTECT(1);
return(dimx);
}
±±±±±±±±±±±±±±±±±±±±±±±±
The question is: how to create pointers to dimx (in order to extract
individual values)?
I tried:
pdimx = REAL(dimx);
This is where R complains that:
REAL() can only be applied to a 'numeric', not a 'integer'
Much in the same line, what would be the procedure to create pointers
to a logical vector y?
I tried:
PROTECT(y = coerceVector(y, LGLSXP));
py = REAL(y);
where R throws a similar error.
Thanks very much in advance,
Adrian
--
Adrian Dusa
Romanian Social Data Archive
1, Schitu Magureanu Bd.
050025 Bucharest sector 5
Romania
Tel.:+40 21 3126618 \
+40 21 3120210 / int.101
Fax: +40 21 3158391
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