Re: pattern in list of derivatives
- To: mathgroup at smc.vnet.net
- Subject: [mg22726] Re: pattern in list of derivatives
- From: Klaus Duellmann <k.duellmann at uni-mannheim.de>
- Date: Fri, 24 Mar 2000 03:27:09 -0500 (EST)
- Organization: Mannheim University
- References: <8b9n7a$997@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Dear Mathgroup Member,
my question from yesterday has already been answered. The (simple)
solution is to use
Cases[{s1}, Derivative[__][u][x,y],-1]
You can get this solution by studying the FullForm of s1.
Remark: The brackets around s1 are unnecessary here.
Thanks to all who have responded!
Klaus Duellmann schrieb:
> I can extract all derivatives from
>
> e.g. s1 = a u'[x] + a u''[x]
>
> by Cases[{s1}, Derivative[_][u][x],-1] and get
>
> {u'[x],u''[x]}
>
> But for mixed derivatives
>
> e.g. {a u[x,y]^(0,1) + c u[x,y]^(1,1)}
>
> the correponding command Cases[{s1}, Derivative[_][u][x,y],-1]
> doesn't work and I receive only the empty list {}.
Klaus Duellmann
Mannheim University
E-mail: k.duellmann at uni-mannheim.de