title: how to concatenate Vectors in Eigen?
body: <p>I have two vectorXd in my program and I like to concatenate them into one vector, so that the second one's values goes after the first one, I found this for matrix but it doesn't seem to work on Vectors:</p>
  
  <p><a href="https://stackoverflow.com/questions/21496157/eigen-how-to-concatenate-matrix-along-a-specific-dimension">Eigen how to concatenate matrix along a specific dimension?</a></p>