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 <javascript:>> 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 <javascript:>. > > To post to this group, send email to sy...@googlegroups.com > <javascript:>. > > 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.