Initialise Eigen::vector with std::vector

Question

I have seen it done before but I cannot remember how to efficiently initialize an Eigen::Vector of known length with a std::vector of the same leng

Answer 1

Just to extend @ggael answer in case others didn't notice it:

From Quick Reference Guide: Mapping External Array:

float data[] = {1,2,3,4};
Map v1(data);       // uses v1 as a Vector3f object
Map  v2(data,3);     // uses v2 as a ArrayXf object
Map m1(data);       // uses m1 as a Array22f object
Map m2(data,2,2);   // uses m2 as a MatrixXf object