As far as I can tell, the function only supports finite differences of one variable at a time. My guess is that it wouldn't be too hard to extend it to do what you want, though.
Aaron Meurer On Thu, Mar 17, 2016 at 7:07 AM, Mathias Louboutin <mathias.loubou...@gmail.com> wrote: > In this example case it would give > > .25 * ( p(x,y+h,z,t) - p(x,y,z,t) + p(x-h,y,z,t) - p(x-y,y+h,z,t) ) /h^2 > > But more generally I would want to be able to take the result of > as_finite_diff as a new expression I can differentiate : > > a = as_finite_diff ( f(.....).diff(x) ) > > b= as_finite_diff( a.diff(y) ) > > ....... And so on > > > Le mercredi 16 mars 2016 21:09:53 UTC, Aaron Meurer a écrit : >> >> What is the answer that you would expect to get? >> >> Aaron Meurer >> >> On Wed, Mar 16, 2016 at 12:12 PM, Mathias Louboutin >> <mathias....@gmail.com> wrote: >> > Hi >> > >> > I am working on PDE's and I am trying to get the symbolic expression for >> > multivariabe finite differences >> > >> > mainly I wan the expression for d/dx(d/dy f), however >> > >> > d2pdxdy=as_finite_diff(p(x,y,z,t).diff(x,y),[x,x-h,y,y+h]) >> > >> > doesn't work, nor any possible combination. Is this just not implemented >> > or >> > am I doing it wrong. >> > >> > cheers >> > >> > mathias >> > >> > -- >> > You received this message because you are subscribed to the Google >> > Groups >> > "sympy" group. >> > To unsubscribe from this group and stop receiving emails from it, send >> > an >> > email to sympy+un...@googlegroups.com. >> > To post to this group, send email to sy...@googlegroups.com. >> > Visit this group at https://groups.google.com/group/sympy. >> > To view this discussion on the web visit >> > >> > https://groups.google.com/d/msgid/sympy/72063849-9fa3-471f-87e4-e5a3b8717255%40googlegroups.com. >> > For more options, visit https://groups.google.com/d/optout. > > -- > You received this message because you are subscribed to the Google Groups > "sympy" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to sympy+unsubscr...@googlegroups.com. > To post to this group, send email to sympy@googlegroups.com. > Visit this group at https://groups.google.com/group/sympy. > To view this discussion on the web visit > https://groups.google.com/d/msgid/sympy/1dafdef7-9a13-4219-a3dc-1c98c45b6c7f%40googlegroups.com. > > For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "sympy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sympy+unsubscr...@googlegroups.com. To post to this group, send email to sympy@googlegroups.com. Visit this group at https://groups.google.com/group/sympy. To view this discussion on the web visit https://groups.google.com/d/msgid/sympy/CAKgW%3D6Kuq-eQoHWoN8Kms2wkLGSvqga1agKpUZKTvpFV9gCwEw%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
