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