更新时间:2023-11-11 23:49:10
使用 armadillo .memptr()
类成员函数,我们能够提取内存指针.在这里,我们可以使用特征的本征矩阵.
现在,我们可以使用特征的内存结构.然后,使用arma::mat
的高级构造函数选项,我们可以创建矩阵.
Now, we can go from the Eigen matrix using the .data()
member function to extract a point to Eigen's memory structure. Then, using the advanced constructor options of arma::mat
we can create an armadillo matrix.
例如:
#include <RcppArmadillo.h>
#include <RcppEigen.h>
// [[Rcpp::depends(RcppEigen)]]
// [[Rcpp::depends(RcppArmadillo)]]
// [[Rcpp::export]]
Eigen::MatrixXd example_cast_eigen(arma::mat arma_A) {
Eigen::MatrixXd eigen_B = Eigen::Map<Eigen::MatrixXd>(arma_A.memptr(),
arma_A.n_rows,
arma_A.n_cols);
return eigen_B;
}
// [[Rcpp::export]]
arma::mat example_cast_arma(Eigen::MatrixXd eigen_A) {
arma::mat arma_B = arma::mat(eigen_A.data(), eigen_A.rows(), eigen_A.cols(),
false, false);
return arma_B;
}
/***R
(x = matrix(1:4, ncol = 2))
example_cast_eigen(x)
example_cast_arma(x)
*/
结果:
(x = matrix(1:4, ncol = 2))
# [,1] [,2]
# [1,] 1 3
# [2,] 2 4
example_cast_eigen(x)
# [,1] [,2]
# [1,] 1 3
# [2,] 2 4
example_cast_arma(x)
# [,1] [,2]
# [1,] 1 3
# [2,] 2 4
一个简短的说明:如果您使用的是Eigen的Mapping功能,那么您应该自动在Armadillo矩阵中进行更改(反之亦然),例如
One quick remark: If you are using Eigen's Mapping function, then you should automatically have the change in the Armadillo matrix (and vice versa), e.g.
#include <RcppArmadillo.h>
#include <RcppEigen.h>
// [[Rcpp::depends(RcppEigen)]]
// [[Rcpp::depends(RcppArmadillo)]]
// [[Rcpp::export]]
void map_update(Eigen::MatrixXd eigen_A) {
Rcpp::Rcout << "Eigen Matrix on Entry: " << std::endl << eigen_A << std::endl;
arma::mat arma_B = arma::mat(eigen_A.data(), eigen_A.rows(), eigen_A.cols(),
false, false);
arma_B(0, 0) = 10;
arma_B(1, 1) = 20;
Rcpp::Rcout << "Armadill Matrix after modification: " << std::endl << arma_B << std::endl;
Rcpp::Rcout << "Eigen Matrix after modification: " << std::endl << eigen_A << std::endl;
}
运行:
map_update(x)
输出:
Eigen Matrix on Entry:
1 3
2 4
Armadill Matrix after modification:
10.0000 3.0000
2.0000 20.0000
Eigen Matrix after modification:
10 3
2 20