message: Return mean, basis and eigenvalues by const& in PcaModel
diff: @@ -113,11 +113,9 @@ public:
  /**
  * Returns the mean of the model.
  *
  - * Todo: Return a const-ref to avoid copying of the vector?
  - *
  * @return The mean of the model.
  */
  - Eigen::VectorXf get_mean() const
  + const Eigen::VectorXf& get_mean() const
  {
  return mean;
  };
  @@ -195,12 +193,9 @@ public:
  * The returned basis is rescaled, i.e. every eigenvector
  * is rescaled by multiplying it with the square root of its eigenvalue.
  *
  - * Returns a copy of the matrix so that the original cannot
  - * be modified. TODO: No, don't return a clone.
  - *
  * @return Returns the rescaled PCA basis matrix.
  */
  - Eigen::MatrixXf get_rescaled_pca_basis() const
  + const Eigen::MatrixXf& get_rescaled_pca_basis() const
  {
  return rescaled_pca_basis;
  };
  @@ -234,7 +229,7 @@ public:
  *
  * @return Returns the orthonormal PCA basis matrix.
  */
  - Eigen::MatrixXf get_orthonormal_pca_basis() const
  + const Eigen::MatrixXf& get_orthonormal_pca_basis() const
  {
  return orthonormal_pca_basis;
  };
  @@ -260,7 +255,7 @@ public:
  *
  * @return The eigenvalues.
  */
  - Eigen::VectorXf get_eigenvalues() const
  + const Eigen::VectorXf& get_eigenvalues() const
  {
  return eigenvalues;
  };
  