def deriv(self, m):
        repNum = self.mesh.vnC[:self.mesh.dim-1].prod()
        repVec = sp.csr_matrix(
                    (np.ones(repNum),
                    (range(repNum), np.zeros(repNum))
                    ), shape=(repNum, 1))
        return sp.kron(sp.identity(self.nP), repVec)
:param numpy.array m: model
dataset/ETHPy150Open simpeg/simpeg/SimPEG/Maps.py/SurjectVertical1D.deriv