Re: Re: NDSolve problem

*To*: mathgroup at smc.vnet.net*Subject*: [mg101701] Re: [mg101676] Re: NDSolve problem*From*: Haibo Min <yshdfeng at gmail.com>*Date*: Wed, 15 Jul 2009 07:06:07 -0400 (EDT)*References*: <h3cfav$ic8$1@smc.vnet.net> <200907140934.FAA01779@smc.vnet.net>

Thank you very much, Simon. After adding the definition, it seems that methematica does recognize the e1,e2 and CurlyTheta and no error indications such as "Part::partw: Part 2 of e1[t] does not exist" occur. EE is in fact a 4x3 matrix. I think my equation is right since I verified all the RHS of the equation (after defining e1,e2 and CurlyTheta respectively) and they are all right. But now new problem occurs, in the NDSolve part, it tells me that: NDSolve::ndode: Input is not an ordinary differential equation. I feel very puzzled, since the equation is INDEED a differential equation with e1,e2 and CurlyTheta as its variables..I checked for many times, but is still to no avail. Could you please help me more to find what the problem is? Thank you again! Best regards, Haibo On Tue, Jul 14, 2009 at 5:34 PM, Simon <simonjtyler at gmail.com> wrote: > Hi Haibo > > Mathematica does not have built in support for abstract linear algebra > quantities, so if something is a vector or a matrix then you have to > give it components. > Define (for example) > e1[t_] := {e11[t], e12[t], e13[t], e14[t]} > e2[t_] := {e21[t], e22[t], e23[t]} > \[CurlyTheta][t_] := {\[CurlyTheta]1[t], \[CurlyTheta]2[t], \ > [CurlyTheta]3[t]} > > Then, the second problem with your code is that the matrices S, G and > J are 3x3, whilst EE is a 4x4 -- you seem to be mixing these in your > differential equations. > For example, the first line in your NDSolve is > J.e2'[t] == -kq Transpose[EE[e1[t]]].e1[t]-... > on the RHS you have a 4-vector minus a whole heap of 3-vectors, on the > LHS a 3-vector. > > Fix these two problems and it should all work.... > > Simon > >

**References**:**Re: NDSolve problem***From:*Simon <simonjtyler@gmail.com>

**RegularExpression bug?**

**Re: Refine, assumptions, domains**

**Re: NDSolve problem**

**Mathematica Special Interest Group (Washington DC Area)**