Rcpp条件中的NA值

Question

我在Rcpp遇到条件问题.解释我的问题的最好方法是通过一个例子.

z <- seq(from=1,to=10,by=0.1)
z[c(5,10,15,20,40,50,80)] <- NA
src <- '
 Rcpp::NumericVector vecz(z);
 for (int i=0;i<vecz.size();i++) {
   if (vecz[i] == NA_REAL) {
     std::cout << "Here is  a missing value" << std::endl;
   }
  }
'
func <- cxxfunction(signature(z="numeric"),src,plugin="Rcpp")
func(z)
# NULL

根据我的理解,NA_REAL表示Rcpp中的实数NA_Integer的NA值,并表示整数的NA值.我不确定为什么上面的条件永远不会返回true给出z.

Answer 1

您可能想要使用RC级别函数R_IsNA.

require(Rcpp)
require(inline)
z <- seq(from=1, to=10, by=0.1)
z[c(5, 10, 15, 20, 40, 50, 80)] <- NA

src <- '
 Rcpp::NumericVector vecz(z);
 for (int i=0; i< vecz.size(); i++) {
   if (R_IsNA(vecz[i])) {
     Rcpp::Rcout << "missing value at position " << i + 1  << std::endl;
   }
  }
'

func <- cxxfunction(signature(z="numeric"), src, plugin="Rcpp")

## results
func(z)

missing value at position 5
missing value at position 10
missing value at position 15
missing value at position 20
missing value at position 40
missing value at position 50
missing value at position 80
NULL