Re: NDSolve[] with nested If[] and Piecewise[] usage:

*To*: mathgroup at smc.vnet.net*Subject*: [mg91397] Re: NDSolve[] with nested If[] and Piecewise[] usage:*From*: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>*Date*: Wed, 20 Aug 2008 04:03:51 -0400 (EDT)*Organization*: The Open University, Milton Keynes, UK*References*: <g8ea0l$4ci$1@smc.vnet.net>

Gopinath Venkatesan wrote: > Sometime back I posted this question on the usage of nested If[] and Piecewise[] inside NDSolve[]. I followed Oliver's reply and was able to solve that particular case. I also could solve another problem which is similar to the posted problem. > > But when I tried the same (like enclosing the expressions with Evaluate[]) on another notebook which has similar usage of nested If[], it did not work. > > I have included the code here, you can also notice that Piecewise[] also did not work here. > > Please give me your suggestions to solve this problem. Thank you. <snip> Apparently, you have forgotten to provide the definitions of the functions v1, v2, and v3. I cannot find any in the posted code nor can NDSolve. ----------- Some parts of the output generated [... snip ...] eqn1 is given by (\[NoBreak]v1[0] (v1^\[Prime])[0] v2[0] \ (v2^\[Prime])[0] v3[0] (v3^\[Prime])[0] \[Phi][0] \ (\[Phi]^\[Prime])[0] 0.533478+3.35388 (-v2[t]+v3[t]-0.67 \ \[Phi][t])-1.65191 (-v1[t]+v3[t]+0.33 \[Phi][t])-0.262758 (-(v1^\ \[Prime])[t]+(v3^\[Prime])[t]+0.33 (\[Phi]^\[Prime])[t])-(\[Phi]^\ [... snip ....] \[Pi]^4 vi[3][t]+1.23953 (vi[3]^\[Prime])[t]+0.155674 (vi[3]^\[Prime]\ \[Prime])[t] \[NoBreak]) Solving the set of equations NDSolve::ndnum: Encountered non-numerical value for a derivative at t \ == 0.`. [... snip ...] ----------------- End of output Regards, -- Jean-Marc