Wall-Crossing Morphisms in Khovanov-Rozansky Homology

We define a wall-crossing morphism for Khovanov-Rozansky homology; that is, a map between the KR homology of knots related by a crossing change. Using this map, we extend KR homology to an invariant of singular knots categorifying the Vasilliev derivative of the HOMFLY polynomial, and of ${\mathfrak{s}\mathfrak{l}}_n$ quantum invariants.