I'm trying to define a matrix $P$ that represents the nodal interpolation operator $\prod_h^{\mbox{curl}}: Q_h^3 \rightarrow V_h$. Here $Q_h$ and $V_h$ are the nodal and Nedelec finite element spaces respectively. The operator $\prod_h^{\mbox{curl}}$ is based on path intergrals along edges; for a finite element function $w_h \in Q_h^3$ is given by
$$\prod_h^{\mbox{curl}} w_h = \sum_j \big( \int_{e_j} w_j \cdot d\vec{s} \big) \psi_j,$$
where $e_j$ is the interior edge associated with the basis function $\psi_j$.
