I am trying to evaluate some nasty derivatives for my splitting scheme. When I tried to do that with Mathematica, I encountered a problem with evaluating an expression of the form below and got an error message.
I would appreciate if anyone could point out how to get the syntax in the first line right in order for Mathematica to evaluate it like the second line.
Simple code input:
In:= f[x] D[g[x, v], v] + v D[g[x, v], x]
In your example, you are using typesetting. This typesetting is obfucasting the issue. Can you type out the actual code? This will make it much more clear what is happening. Write it out using the D and Derivative expressions.
Derivative expressions don't have addition defined on them. You could define that. Or you could just write out your new operator as a function:
myOperator[f_] := (Derivative[0, 1][f] + Derivative[1, 0][f]);
thank you for the very helpful example. This was what I was looking for.