Re: Replace not spotting a replacement
- To: mathgroup at smc.vnet.net
- Subject: [mg103582] Re: [mg103399] Replace not spotting a replacement
- From: "David Carter-Hitchin" <david at carter-hitchin.clara.co.uk>
- Date: Tue, 29 Sep 2009 07:37:41 -0400 (EDT)
- References: <200909201021.GAA24204@smc.vnet.net> <20090920101230.QC4SM.18877.imail@eastrmwml39>
Hi Bob, Thanks - I'll bear this approach in mind. Use solve to simplify the rule first. Thanks, David. > -----Original Message----- > From: Bob Hanlon [mailto:hanlonr at cox.net] > Sent: 20 September 2009 15:13 > To: mathgroup at smc.vnet.net; claranet news > Subject: Re: [mg103399] Replace not spotting a replacement > > > Make the LHS of a rule as simple as possible > > sub = Solve[Equal @@ (Sqrt[2*Pi*\[Tau]] -> \[Mu]), \[Tau]][[1]] > > {\[Tau] -> \[Mu]^2/(2*Pi)} > > Simplify[Sqrt[2*Pi]*\[Tau]^(3/2) /. sub, > Element[\[Mu], Reals]] > > Abs[\[Mu]]^3/(2*Pi) > > Simplify[Sqrt[2*Pi]*\[Tau]^(3/2) /. sub, > \[Mu] >= 0] > > \[Mu]^3/(2*Pi) > > > Bob Hanlon > > ---- claranet news <david at carter-hitchin.clara.co.uk> wrote: > > ============= > Hi Folks, > > Seems the replace function is being a bit dim here. This fails: > > Sqrt[2 \[Pi]] \[Tau]^(3/2) /. Sqrt[ 2 \[Pi] \[Tau]] -> \[Mu] > > Apologies if this is an FAQ - I couldn't see anything about it. What > do I > need to do here to coerce Mathematica into making this replacement? I > tried using the > Collect function on tau first, but that didn't seem to work. I also > tried > re-writing the replacement rule as > > Sqrt[2 \[Pi]] \[Tau]^(3/2) /. Sqrt[ 2 \[Pi] ] t^(1/2) -> \[Mu] > > But still no joy. > > Anyone know? > > Many thanks, > David. > > > No virus found in this incoming message. > Checked by AVG - www.avg.com > Version: 8.5.409 / Virus Database: 270.13.111/2386 - Release Date: > 09/21/09 05:51:00
- References:
- Replace not spotting a replacement
- From: "claranet news" <david@carter-hitchin.clara.co.uk>
- Replace not spotting a replacement