RcppParallel:将 CharacterMatrix 转换为 RMatrix<T> [英] RcppParallel: Converting CharacterMatrix to RMatrix&lt;T&gt;

问题描述

亲爱的社区，您好，

我正在学习 RcppParallel 并在尝试使用以下代码将 Rcpp::CharacterMatrix 转换为 RcppParallel::RMatrix 时遇到此问题:

I am learning RcppParallel and have this issue while trying to convert a Rcpp::CharacterMatrix to RcppParallel::RMatrix using following codes:

struct CharMatDist : RcppParallel::Worker {
    const RcppParallel::RMatrix<std::string> A; 
    const RcppParallel::RMatrix<std::string> B; 
    const NumericVector w; 
    RcppParallel::RMatrix<double> ret; 
    int n; 

    CharMatDist(CharacterMatrix A, CharacterMatrix B, NumericVector w, NumericMatrix ret)
    : A(A), B(B), w(w), ret(ret) {
        n = B.nrow();
    }

...

}

正如画廊所建议的，我希望在 A(A) 等中自动进行转换，但它不起作用并给我以下错误:

As the gallery suggests, I would expect the convertion to be carried out automatically in A(A) etc. but it is not working and gives me following error:

cannot convert 'Rcpp:Matrix<16>::iterator (aka Rcpp::internal::Proxy_iterator<Rcpp::internal::string_proxy<16> >)' to 'char*' in initialization

我也试过

RMatrix<char>

甚至手动cast in body 也没有成功.我哪里做错了??

and even manual cast in body but also without success. Where am I doing wrong??

任何建议和帮助将不胜感激.

Any suggestions and help would be highly appreciated.

YYA

推荐答案

这里的问题是 CharacterVector 和 CharacterMatrix 类型实际上只是 SEXPs -- 更具体地说，一个 CharacterVector 包装了一个 STRSXP，其内容是一个 SEXP 数组(运行时类型为 CHARSXP).不幸的是，在与 R 的字符类型交互时，了解这些细节是必要的.

The issue here is that CharacterVector and CharacterMatrix types are really just vectors of SEXPs -- more specifically, a CharacterVector wraps a STRSXP, whose contents is an array of SEXPs (of runtime type CHARSXP). Unfortunately, knowing these details is necessary when interacting with R's character types.

我不知道这是否可行，但如果可行，您会想要使用类似 RMatrix<SEXP> 之类的东西，它(推测)会映射底层 CHARSXP 位于矩阵内部——您可以在其中使用 CHAR 访问带下划线的 const char* 字符串.

I have no idea if this will work, but if it did, you'd want to use something like an RMatrix<SEXP>, which would (presumedly) map over the underlying CHARSXPs inside the matrix -- wherein you could access the underlining const char* string with CHAR.

不幸的是，RMatrix 类不够聪明"，无法在这种情况下直接提供对底层字符串的访问，所以我相信您必须自己解开它.

The RMatrix class is not 'smart' enough to directly provide access to the underlying strings in this case, unfortunately, so I believe you will have to unwrap it yourself.

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