RE: collect derivatives

*To*: mathgroup at smc.vnet.net*Subject*: [mg23294] RE: [mg23259] collect derivatives*From*: "David Park" <djmp at earthlink.net>*Date*: Sun, 30 Apr 2000 21:13:44 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

> From: Robert [mailto:robert.schuerhuber at gmx.at] To: mathgroup at smc.vnet.net > > is there a way to use "collect[]" to collect all terms with a specific > derivative, e.g. to produce something like > > z''[x] u[x] + z'[x] (u'[x]+u[x]) + z[x] > > ? > > thanks, robert Robert, Easy! e1 = z''[x] u[x] + z'[x] (u'[x] + u[x]) + z[x] // Expand; Collect[e1, {Derivative[_][z][x]}] z[x]+(u[x] + u'[x])z'[x] + u[x]z''[x] David Park djmp at earthlink.net http://home.earthlink.net/~djmp/