How to solve divergence (gradient(column matrix))

Apart from applying L2 norm, it's derivative so called L1 is applied for edges of a image. for image I, size M*N f be the column matrix MN*1 then ∇∙(∇f)/|∇f | where (∇f) is gradient, |∇f | L1 norm of (∇f) but the problem is ,since f is column matrix , divergence function in matlab is gives error saying that the matrix must be 2*2 or greater. how to overcome this problem?

[Jan]

Please edit the question and insert some code, which reproduces the problem. Then add a copy of the error message, because a rought paraphrasation might conceal important details.