[dune-fem] Calculating the gradient of an AdaptiveDiscreteFunction

[Alasdair James McLeay]

Hi,

I need to calculate the gradient or jacobian of the solution to a 1D problem at specific points. The solution type is AdaptiveDiscreteFunction and I'm looking for the best way to calculate the gradient.

I see there is a function .jacobian(x, ret) but unfortunately this seems to return a 'not implemented' error so guess I'll need to look for something else. I've had a look at 'dgmasspass.hh' but can't figure out how to use it or see any examples of it's use. 

I also see that PDELabs offers some helper functions that I may be able to use.

Does anyone have a suggestion as to the best route?

Thanks,
Ali