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MathGroup Archive 2000

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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/ 


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