# differential equations – Taking mean of a numerical function \$f(t’,x,y)\$

$$f(t,x,y)$$ is a solution from NDSolve, in a domain $$mathcal{D}$$.

If $$f(t,x,y)$$ was an analytical func I would

$$overline{f(t)}=frac{ int _{mathcal{D}} f(t,x,y) dx dy}{mathcal{D}}$$

Since $$f(t,x,y)$$ is number for each x point, how can one compute its average value in the domain for a certain $$t=t’$$? It is basically taking the mean of $$f(t’,x,y)$$ in the domain but I couldn’t figure out how to do it.