[firedrake] Initial conditions in a mixed function space

Dear all, I hope I have not missed something obvious again but I'm looking to assign initial conditions for my variables \underline{u} , \rho and p. Velocity, density and pressure respectively. I have a mixed function space W, and my first thought was to define initial variables by splitting a W function w_ = Function(W) (u_, r_, p_) = split(w_) and then interpolating my expression for the exact solution for each variable u_.sub(0).interpolate(exact_w) r_.interpolate(exact_r) but as I get the error File "compressible.py", line 74, in <module> r_.interpolate(exact_r) AttributeError: 'Indexed' object has no attribute 'interpolate' this is clearly not the way to go. What would be a better approach ? Will