[R] I can't make .C(...) web-page example.
Prof Brian Ripley
ripley at stats.ox.ac.uk
Sun Feb 1 16:22:47 CET 2004
Change the name. There is a convolve C function in R 1.8.x (but not
R-devel) that is being found rather than yours.
On Sun, 1 Feb 2004, Ricardo Zorzetto Nicoliello Vencio wrote:
>
> Hi everyone!
>
> I'm trying to lear how to call external C code in R but even the R help
> web-page example is drive me crazy.
>
> I copy-paste the example at:
>
> http://stat.ethz.ch/R-manual/R-patched/doc/manual/R-exts.html#Interface%20functions%20.C%20and%20.Fortran
>
> here is the example:
>
> void convolve(double *a, int *na, double *b, int *nb, double *ab)
> {
> int i, j, nab = *na + *nb - 1;
>
> for(i = 0; i < nab; i++)
> ab[i] = 0.0;
> for(i = 0; i < *na; i++)
> for(j = 0; j < *nb; j++)
> ab[i + j] += a[i] * b[j];
> }
>
> called from R by
>
> conv <- function(a, b)
> .C("convolve",
> as.double(a),
> as.integer(length(a)),
> as.double(b),
> as.integer(length(b)),
> ab = double(length(a) + length(b) - 1))$ab
>
>
> but using the conv function in simple examples give me trouble:
>
> > conv(1:10,2:11)
> Error in conv(1:10, 2:11) : pairlist object cannot be coerced to double
>
> > conv( rnorm(10,10,1) , rnorm(10,11,1) )
> Segmentation fault
>
> > conv( c(10.53, 8.456, 6.6) , c(10.53, 8.456, 6.6) )
> Error in conv(c(10.53, 8.456, 6.6), c(10.53, 8.456, 6.6)) :
> cannot allocate vector of length 1717986918
>
> > a = c(1.46756, 5.56456, 2.3646)
> > b = a + 5.4
> > conv(a,b)
> Error in conv(a, b) : cannot coerce type promise to double vector
>
>
> and so on.
>
> These results appear if I have only the .c file or if I use gcc -c conv.c
> to create .o file. I cannot create executable because there is no
> main(...) in .c file but just the copy-pasted example.
>
>
> Someone knows what is happening to me ?
>
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>
--
Brian D. Ripley, ripley at stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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