Hey cyberbaffled.

Consider that when you differentiate something then everything that isn't relative to the independent variable is treated as a constant.

Lets say you have w = f(x0,x1,x2) and you only want to differentiate against x, then if you only want df/dx^0 you can use tensor notation to mask this out by using d_(m,0)*df/dx^m where m is a dummy variable and d_(m,0) is the kronecker delta function where d_(x,y) = 1 if x=y and 0 otherwise.