Mathematica Error explanation in the function NDSolve in mathematica 8

[Nesrine]

Hello ,

I have tried to solve a system of differentiel equations with mathematica that is presented as follow

X[t_] = {x1[t], x2[t], x3[t], x4[t], x5[t], x6[t] , x7[t], x8[t],
x9[t], x10[t], x11[t], x12[t]};
system = MapThread[#1 == #2 &, {X'[t], A.X[t]}];

where the matrix A is periodic.

when I used NDSolve :

sol = NDSolve[{system,
x1[0] == x2[0] == x3[0] == x4[0] == x5[0] == x6[0] == x7[0] ==
x8[0] == x9[0] == x10[0] == x11[0] ==
x12[0] == {1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1}}, {x1, x2, x3, x4,
x5, x6, x7, x8, x9, x10, x11, x12}, {t, 0, T}];

I have got an error message that is :

NDSolve::ndfdmc: Computed derivatives do not have dimensionality consistent with the initial conditions. >>

Can someone please explain it to me??

Thank you very much

 

[Bill Simpson]

Show us what value your 'system' variable has when you are doing that.

Seeing exactly what NDSolve is actually being given might answer the question.

Are you saying that each of your x1[0],x2[0]... are all equal to a vector of 12 1's?
Or are you thinking that each of your x1[0],x2[0]... are each equal to 1?