How to make rules for changing parameters

Question

I have one boring problem with changing parameters in printing output. If I have equation

    eq = Plus[Times[a1,Derivative[2,0][q2][x,y]],Times[a2,Derivative[3,1][q1][x,y]]];

I want to replace all derivatives with new variables, for example this

      Derivative[2, 0][q2][x, y]

I want to replace it with $C_{\mathrm{q2}}^{2,0}$ and for all of them on the same way to get eq output automatically in this form

$\mathrm{a1}\,C_{\mathrm{q2}}^{2,0}+\mathrm{a2}\,C_{\mathrm{q1}}^{3,1}$

Answer 1

If I understand you correctly, this might be what you're looking for:

eq /. Derivative[n__][q_][__] :>
            RawBoxes[
                 SubsuperscriptBox["C",
                                   ToString[q],
                                   RowBox[Riffle[{n}, ","]]
              ]]

Please note the using of SubsuperscriptBox and RawBoxes, which will prevent superscript being evaluated as Power.