ja1.cpp

// std::vector<Eigen::VectorXf> -> Eigen::MatrixXf
#include <iostream>
#include <vector>
#include <Eigen/Dense>

int main() {
    using namespace Eigen;
    const int cols = 10;
    const int rows = 10;  // or do you get it from the sizes of each entry in *d?
    std::vector<VectorXf> * d = new std::vector<VectorXf>(cols);
    for (int col = 0; col < cols; ++col) {
        (*d)[col] = VectorXf(rows);
        (*d)[col].setRandom();
    }

    // now create the Matrix and copy from vector of vectors
    Matrix<float, Dynamic, Dynamic> result(rows, cols);   // assuming we know #rows...
    for (int col = 0; col < cols; ++col) {
        result.col(col) = (*d)[col];
    }
            
    IOFormat OctaveFmt(StreamPrecision, 0, ", ", ";\n", "", "", "[", "]");
    std::cout << "result matrix=\n" << result.format(OctaveFmt) << "\n";
}

// Ended up with this
    Eigen::Matrix< float, Eigen::Dynamic, Eigen::Dynamic > ev(d->size(), 128);
    for ( int r = 0; r < d->size(); ++r ) {
        for (int c = 0; c < 128; ++c) {
            ev(r,c) = (*d)[r](c);
        }
    }

Thanks.