r - Error in using Rcpp in Rmarkdown -

i want compare speed of ordinary r-loop , loop rcpp. need comparison small documentation , that's why have in use in rmarkdown. code is:

for_r <- function(n){   <- 0   for(i in 1:n){     = +   }   return(a) }  rcpp::cppfunction('         int for_c(int n) {           int = 0;           for(int = 1; < (n+1); i++) {             += i;           }           return a;         }', showoutput = true)  microbenchmark::microbenchmark('r-schleife' = for_r(10000),                                'c-schleife' = for_c(10000)) 

the output cppfunction is:

## c:/progra~1/r/r-32~1.1/bin/x64/r cmd shlib -o "sourcecpp_71184.dll" "" "file30c7c6b798b.cpp" 

i'm little bit confused following error appears when knitr file:

## error in sourcecpp(code = code, env = env, rebuild = rebuild, showoutput = showoutput, : error 1 occurred building shared library. 

if run code in console works fine , without error. try knitr rmd file different directions, failed.

some information software:

• r version 2.3.1
• rtools installed in c:
• i use in combination rstudio version 0.99.465

i searched in other posts, everytime found error wasn't in rmarkdown. installed new operating system (windows 8.1) , after finishing , install programms error occurs. happy if help.

your code builds me (under linux). i'd use sourcecpp() , put in .cpp file:

#include <rcpp.h>  // [[rcpp::export]] int for_c(int n) {   int = 0;   for(int = 1; < (n+1); i++) {     += i;   }   return a; }  /*** r for_r <- function(n) {   <- 0   for(i in 1:n){     = +   }   return(a) }  microbenchmark::microbenchmark('r-schleife' = for_r(10000),                                'c-schleife' = for_c(10000)) */ 

which, when sourcecpp()-ed, produces result:

r> sourcecpp("/tmp/daniel.cpp")  r> for_r <- function(n) { +   <- 0 +   for(i in 1:n){ +     = + +   } +   return(a) + }  r> microbenchmark::microbenchmark('r-schleife' = for_r(10000), +                                'c-schleife' = for_c(10000)) unit: microseconds        expr      min       lq       mean   median       uq       max neval  r-schleife 4351.736 4680.954 6300.95103 4774.863 5166.111 70614.405   100  c-schleife    5.457    6.618    9.80134    9.746   11.471    50.236   100 r>