CODEWITHSUNDEEP
c++eigen
Manish
Manish

Reputation: 738

typecasting Eigen::VectorXd to std::vector

Their are many links to go the other way round but I am unable to find to get a std::vector from a Eigen::Matrix or Eigen::VectorXd in my specific case.

Upvotes: 52

Views: 55481

Answers (3)

Bastienm
Bastienm

Reputation: 393

You can do this from and to Eigen vector : 

    //init a first vector
    std::vector<float> v1;
    v1.push_back(0.5);
    v1.push_back(1.5);
    v1.push_back(2.5);
    v1.push_back(3.5);

    //from v1 to an eignen vector
    float* ptr_data = &v1[0];
    Eigen::VectorXf v2 = Eigen::Map<Eigen::VectorXf, Eigen::Unaligned>(v1.data(), v1.size());

    //from the eigen vector to the std vector
    std::vector<float> v3(&v2[0], v2.data()+v2.cols()*v2.rows());


    //to check
    for(int i = 0; i < v1.size() ; i++){
        std::cout << std::to_string(v1[i]) << " | " << std::to_string(v2[i]) << " | " << std::to_string(v3[i]) << std::endl;
    }

Upvotes: 2

ggael
ggael

Reputation: 29205

You cannot typecast, but you can easily copy the data:

VectorXd v1;
v1 = ...;
vector<double> v2;
v2.resize(v1.size());
VectorXd::Map(&v2[0], v1.size()) = v1;

Upvotes: 64

John Zwinck
John Zwinck

Reputation: 249133

vector<int> vec(mat.data(), mat.data() + mat.rows() * mat.cols());

Upvotes: 68

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