本征将矩阵转换为矢量 [英] Eigen Convert Matrix to Vector

问题描述

在 MATLAB 中，下面的行将Matrix转换为Vector.它将矩阵逐列展平为vector.

In MATLAB, the line below converts a Matrix to a Vector.It flattens the matrix column by column into a vector.

myvar(:)

我应该如何使用Eigen来做到这一点?该解决方案应适用于任何尺寸的Matrix.

How do I do that with Eigen? The solution should work for any dimension of Matrix.

MatrixXd A(3,2);
VectorXd B(6);
A << 1,2,3,4,5,6;
B << A.col(0), A.col(1); 
//This isn't general enough to work on any size Matrix

推荐答案

本征矩阵默认情况下按列主顺序存储，因此您可以使用本征映射将数据逐列存储在数组中:

Eigen matrices are stored in column major order by default, so you can use simply use Eigen Maps to store the data column by column in an array:

MatrixXd A(3,2);
A << 1,2,3,4,5,6;
VectorXd B(Map<VectorXd>(A.data(), A.cols()*A.rows()));

如果要按行对数据进行排序，则需要先对矩阵进行转置:

If you want the data ordered row by row, you need to transpose the matrix first:

MatrixXd A(3,2);
A << 1,2,3,4,5,6;
A.transposeInPlace();
VectorXd B(Map<VectorXd>(A.data(), A.cols()*A.rows()));

这篇关于本征将矩阵转换为矢量的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！