Expand_derivatives vs derivative?

[ejmeitz]

What's the difference between expand_derivatives and derivative (which I assume is equivalent to the Differential approach)? With expand_derivatives I get an error Differentiation with array expressions is not yet supported but if I define differentials the derivative gets calculated. There's no doc-string for expand_derivatives so I'm not 100% sure what its supposed to do but I would have expected this code to work.

My variables are: @variables ri[1:3] rj[1:3] rk[1:3] The derivative I defined is: D = Differential(ri[1]) * Differential(rj[1]) D(<eqn>) The expand_derivative command I used: expand_derivatives(D(<eqn>))