[英]How to convert row vector to column vector in Eigen?
The documentation says: 文件说:
... in Eigen, vectors are just a special case of matrices, with either 1 row or 1 column.
...在Eigen中,向量只是矩阵的一个特例,有1行或1列。 The case where they have 1 column is the most common;
他们有1列的情况是最常见的; such vectors are called column-vectors, often abbreviated as just vectors.
这种矢量称为列矢量,通常缩写为矢量。 In the other case where they have 1 row, they are called row-vectors.
在他们有1行的另一种情况下,它们被称为行向量。
However this program outputs unintuitive results: 但是,该程序输出的结果不直观:
#include <eigen3/Eigen/Dense>
#include <iostream>
typedef Eigen::Matrix<double, 1, Eigen::Dynamic> RowVector;
int main(int argc, char** argv)
{
RowVector row(10);
std::cout << "Rows: " << row.rows() << std::endl;
std::cout << "Columns: " << row.cols() << std::endl;
row.transposeInPlace();
std::cout << "Rows: " << row.rows() << std::endl;
std::cout << "Columns: " << row.cols() << std::endl;
}
Output: 输出:
Rows: 1
Columns: 10
Rows: 1
Columns: 10
Is this a bug, or am I using the library incorrectly? 这是一个错误,还是我错误地使用了库?
The documentation for transposeInPlace
says: transposeInPlace
的文档说:
Note
注意
if the matrix is not square, then
*this
must be a resizable matrix.如果矩阵不是正方形,则
*this
必须是可调整大小的矩阵。
You'll need your type to have both dynamic rows and columns: 您需要您的类型同时拥有动态行和列:
Eigen::Matrix<double, Eigen::Dynamic, Eigen::Dynamic>
However, there's already a typedef
for this: MatrixXd
. 但是,已有一个
typedef
: MatrixXd
。
Alternatively, if you still want the compile-time sizes, you can use tranpose
rather than transposeInPlace
to give you a new transposed matrix rather than modify the current one: 或者,如果您仍然需要编译时大小,则可以使用
tranpose
而不是transposeInPlace
为您提供新的转置矩阵,而不是修改当前的矩阵:
typedef Eigen::Matrix<double, Eigen::Dynamic, 1> ColumnVector;
ColumnVector column = row.transpose();
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