[英]sample in Rcpp Armadillo
I am currently struggeling with the sample() command provided in RcppArmadillo
. 我目前正与提供的样本()命令struggeling
RcppArmadillo
。 When I try to run the code below I get the error no matching function for call to sample
and I already add the extra Rcpp::
namespace in front since this worked out well in another post . 当我尝试运行下面的代码时,出现错误,
no matching function for call to sample
并且我已经在前面添加了额外的Rcpp::
名称空间,因为这在另一篇文章中很好地解决了。
I also tried several other container classes, but I am always stuck with this error. 我也尝试了其他几个容器类,但是我总是被这个错误困扰。 Below is some code, which produces the error.
下面是一些代码,它会产生错误。
Any help would be greatly appreciated :) 任何帮助将不胜感激 :)
#include <RcppArmadillo.h>
// [[Rcpp::depends(RcppArmadillo)]]
#include <RcppArmadilloExtensions/sample.h>
using namespace Rcpp;
// [[Rcpp::export]]
NumericMatrix example(arma::mat fprob,
int K) {
int t = fprob.n_rows;
IntegerVector choice_set = seq_len(K);
arma::mat states(t,1); states.fill(0);
arma::rowvec p0(K);
arma::rowvec alph(K);
double fit;
p0 = fprob.row(t-1);
fit = accu(p0);
alph = p0/fit;
states(t-1,1) = Rcpp::RcppArmadillo::sample(choice_set, 1, false, alph)[0];
return wrap(states);
}
Here the definition of that function from the header: 这里从头开始定义该函数:
// Enables supplying an arma probability
template <class T>
T sample(const T &x, const int size, const bool replace, arma::vec &prob_){
return sample_main(x, size, replace, prob_);
}
Note that it expects a arma::vec == arma::colvec
, while you are providing a arma::rowvec
. 请注意,当您提供
arma::rowvec
,它期望arma::vec == arma::colvec
arma::rowvec
。 So it should work if you change p0
and alph
to arma::vec
. 因此,如果将
p0
和alph
更改为arma::vec
它应该可以工作。 Untested because of missing sample data ... 由于缺少样本数据而未经测试...
BTW, there is meanwhile also a Rcpp:::sample()
function in case you are not really needing Armadillo for other tasks. 顺便说一句,同时还有
Rcpp:::sample()
函数,以防您真的不需要Armadillo来完成其他任务。
Concerning the performance questions raised by @JosephWood in the comments: I have the impression that both Rcpp::sample()
and Rcpp::RcppArmadillo::sample()
are based on do_sample()
. 关于@JosephWood在评论中提出的性能问题:我的印象是
Rcpp::sample()
和Rcpp::RcppArmadillo::sample()
都基于do_sample()
。 So they should be quite similar in most cases, but I have not benchmarked them. 因此,它们在大多数情况下应该非常相似,但我尚未对其进行基准测试。 The higher performance of R for unweighted sampling without replacement for larger numbers comes from the hash algorithm , which is selected at R level in such cases.
R在未加权采样的情况下具有更高的性能,而无需替换较大的数字,这得益于在这种情况下在R级别选择的哈希算法 。 It is also interesting to note that R 3.6 will have a new method for sampling in order to remove a bias present in the current method.
还有趣的是,R 3.6将具有一种新的采样方法,以消除当前方法中存在的偏差。
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