Re: changing replacement rule arrow ( ->) to equal sign(==)...

*To*: mathgroup at smc.vnet.net*Subject*: [mg45890] Re: changing replacement rule arrow ( ->) to equal sign(==)...*From*: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>*Date*: Thu, 29 Jan 2004 05:34:36 -0500 (EST)*Organization*: Universitaet Leipzig*References*: <bv83l0$idm$1@smc.vnet.net>*Reply-to*: kuska at informatik.uni-leipzig.de*Sender*: owner-wri-mathgroup at wolfram.com

Hi, {G[0] -> 4*(5 - 2*Sqrt[6]), tfC[0] -> 2*(5 - 2*Sqrt[6]), C[0] -> 3 - Sqrt[6], tf[0] -> 3 - Sqrt[6]} /. Rule->Equal may help you. Regards Jens sean kim wrote: > > thanks for all those tho replied regarding adding interpoating > functions. > > few more questions... > > let's say you can Solve a system of equations like this. > > In[267]:= > itxn = Solve[{0 == 1 - 2C[t] - 1 C[t] tf[t] + 2 tfC[t], > 0 == -1 G[t] + 2 tfC[t], > 0 == 1 - 2 tf[t] - 1 C[t] tf[t] + 2 tfC[t], > 0 == 1 C[t] 2 tf[t] - 1 tfC[t] - 2 tfC[t]}, {C[t], G[t], > tf[t], > tfC[t]}][[1]] /. t -> 0 > > above give a replacement rule as below. > > {G[0] -> 4*(5 - 2*Sqrt[6]), tfC[0] -> 2*(5 - 2*Sqrt[6]), > C[0] -> 3 - Sqrt[6], tf[0] -> 3 - Sqrt[6]} > > now I would like to use this rule asd part of NDSolve as initial > conditions. but as we all know, it can't be used directly. > > the -> needs to be replaced with == > > now, if i try to Map a rule that replaces -> with ==, like... > > Map[{itxn[[1]] == itxn[[2]]}, itxn] > > it doesn't work. > > it gives a long list with wrong result. > > what i wanted though is > {G[0] == 4*(5 - 2*Sqrt[6]), tfC[0] == 2*(5 - 2*Sqrt[6]), > C[0] == 3 - Sqrt[6], tf[0] == 3 - Sqrt[6]} > > So, what i would like to do is use the results from the Solve directly > in NDSolve as the initial conditions without having to manually edit > out the arrows with equal signs. > > can you guys please shed some light on this matter? > > thank you very much in advance > > sean