Rcpp Errror

[Kamel20]

Hello everyone,
I am trying to speed up my code by using Rcpp, the last function in this code (myModel) makes a problem for me, when I compile the code, I get this error,

1. cannot convert 'SEXP {aka SEXPREC*}' to 'Rcpp:traits::input_parameter::{aka Rcpp::InputParameter}' in initialization
2. cannot convert 'Rcpp::traits::input_parameter::type{aka Rcpp::InputParameter}' to 'double*' for argument '3' to double myModel(double, int, double*, int)
   could anyone helps me for that,

#include <Rcpp.h>
#include <math.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include
using namespace Rcpp;
// Place the export tag right above function declaration.
// [[Rcpp::export]]
double FactorialC(int n)
{
int ii;
double prod;
if(n==0) return 1;
if(n==1) return 1;
prod=1.0;
for(ii=n; ii>0; ii--) prod *= ii;
return prod;
}
// [[Rcpp::export]]
double PoissonKC(double mu, int n)
{
double prob;
if(n==0) return (exp(-1.0*mu));
prob = (exp(-1.0*mu)*pow(mu,n))/FactorialC(n);
return prob;
}
// [[Rcpp::export]]
double myModel(double d, int m, double Vin, int flag){
double Vout, mu, probk;
int kk, jj, H,R;
Vout = (double) calloc(m+1, sizeof(double));
mu = 2(m+1)*d;
for(kk =0; kk<= 50; kk++){
probk = PoissonKC(mu, kk);
for(jj =0; jj<=m; jj++){
  if(kk>0){
    H = (jj + kk)/(m+1);
    R = (jj + kk)%(m+1);
    if(H >0){
      Vout[R] += 0.5*Vin[jj]*probk;
    }
    else{
      if(flag == 2) Vout[R] += Vin[jj]*probk;
    }
  }
  else{
    if(flag == 2) Vout[jj] += Vin[jj]*probk;
  } 
}
}
Vout;
}

[eddelbuettel]

Please follow the link in the edit box to learn about formatting. It is not hard. See other questions or issue tickets where you drop into edit mode. Thank you.

[kevinushey]

cannot convert 'Rcpp::traits::input_parameter::type{aka Rcpp::InputParameter}' to 'double*' for argument '3' to double myModel(double, int, double*, int)

This does not match the code you copied here. The error suggests that your function accepts a double* parameter (pointer to double), but the code you copied just uses a plain double.

I'm guessing that Rcpp Attributes does not understand how to marshal to double*. But the solution here is pretty simple: just use NumericVector instead, or pass a SEXP and get the data pointer with e.g. REAL(data).

[eddelbuettel]

There is no real issue with Rcpp here -- you just need to learn a little about how to use it. Please see the Rcpp Gallery (and if needed reset some links to http, as https it does not always render right) and maybe also the mailing list archives as well as StackOverflow.