change of variables in PDE?

*To*: mathgroup at smc.vnet.net*Subject*: [mg8834] change of variables in PDE?*From*: Geoffrey Simms <gdsimms at uiuc.edu>*Date*: Mon, 29 Sep 1997 02:40:00 -0400*Organization*: University of Illinois at Urbana-Champaign*Sender*: owner-wri-mathgroup at wolfram.com

I hope this isn't too trivial a question... I am trying to change variables in a PDE f[x_,y_] -> F[X,Y] where the new variables and functions are defined like, e.g.: X = x^2 + y Y = 2 + x y F = x f I would like Mathematica to recognize f and all of its partial derivatives, applying the chain rule where necessary, etc. to a PDE given in terms of f, x, and y, returning the PDE in terms of F, X, and Y, with all derivatives fixed accordingly. It seems that this would be a common request, and yet in all my searcing I haven't found a way to do this. Is there a package anyone knows about that does this? Thank you, Geoff Simms