Re: NDSolve problem

*To*: mathgroup at christensen.cybernetics.net*Subject*: [mg912] Re: NDSolve problem*From*: saarinen (Sirpa Saarinen)*Date*: Sun, 30 Apr 1995 03:46:37 -0400*Organization*: Wolfram Research, Inc.

In <3nkcth$n02 at news0.cybernetics.net> pitts at mayo.EDU (Todd Pitts) writes: >Changing the coefficient 4.0 in eq to unity (1 not 1.0) gives no error. Also >writing the equation as >eq={D[x[1][t],{t,2}]==(x[1][t]-Sin[t])/4}; >works. If I don't use subscripted variables I don't have this problem. For >example >sys2 = sys /. x[1] -> x >NDSolve[sys2,x,{t,0,10}] >seems to work fine. I would greatly appreciate any hints. Is this a bug or >have I misunderstood the use of subscripted variables? The version number is >2.2. I get the same behavior on NeXT and DEC Alfa. The current version V2.2 of NDSolve does not support indexed variables, so you could use something like Out[6]= {x''[t] == -Sin[t] + x[t], x'[0] == 0, x[0] == 0} In[7]:= In[7]:= NDSolve[sys,x,{t,0., 10.}] Out[7]= {{x -> InterpolatingFunction[{0., 10.}, <>]}} In the version under development most N* functions in mathematica will be supporting also indexed variables. Sirpa Saarinen saarinen at wri.com