```Date: Jul 12, 2011 6:09 AM
Author: Iván Lazaro
Subject: Re: Incredible slow Plot

Well, i'm going to try to clarify it a little, but, as I said, is notposible to paste the complete code; the equations are just too big. Ialso made a mistake writing the last email.So, for example,{eqns, cond}={f1'[t]==a11*f1[t]+a12*f2[t]+...+a1N*fN[t],...,fN'[t]==aN1*f1[t]+aN2*f2[t]+...+aNN*fN[t], f1[0]==t01,...,fN[0]==t0N},andf={f1,f2,...,fN}.If Something is, say 1, thensol[[1, 1]]:f1[t]->InterpolatingFunction[{{0.`,1200.`}},"<>"][t]and  sol[[1, 1, 2]] is just InterpolatingFunction[{{0.`,1200.`}},"<>"][t].So, withsol=NDSolve[{eqns, cond},f,{t,0,1200}][[1]];a[t_]=sol[[1, 1, 2]]b[t_]=sol[[1, 2, 2]]i'm just extracting the solution for two of my variables, f1 and f2.Plot "a" and "b",Plot[{a[t], b[t]},{t,0,1200}],was fast; however this:Plot[{Evaluate[f1[t]/.sol], Evaluate[f2[t]/.sol]},{t,0,1200}],was, somehow, imposible.2011/7/11 DrMajorBob <btreat1@austin.rr.com>:>> and that was it. However I don't understand this. Was the problem the>> "size" and "amount" of interpolated functions?>> I don't understand it either. The two methods seem equivalent, but this code>>> sol=NDSolve[{eqns, cond},f,{t,0,1200}][[1]];>> a=sol[[1, Something, 2]]>> b=sol[[1, Something+1, 2]]>> suggests that you're solving for one function f in the first line, and YET,> you're extracting two solutions a and b in the next two lines. That's not> possible, so you're not showing us the code you actually used. (We know that> anyway, since "eqns", "cond", and "Something" are undefined.)>> I suspect in the real code, the two methods that seem equivalent are NOT> equivalent at all.>> Bobby>> On Mon, 11 Jul 2011 05:58:03 -0500, Iv=E1n Lazaro <gaminster@gmail.com> wrote:>>> Hi!>>>> Yes, I tried>>>>  sol=NDSolve[{eqns, cond},f,{t,0,1200}][[1]];>>  Plot[Evaluate[f[t]/.sol],{t,0,1200}],>>>> but that was a pain. Thanks to Bobby I managed to solve my speed problem:>>>> Instead of>>>> sol=NDSolve[{eqns, cond},f,{t,0,1200}][[1]];>> Plot[Evaluate[f[t]/.sol],{t,0,1200}],>>>> I selected the specific solutions I needed, and Set them to a variable>> that then I plot:>>>>>>>> sol=NDSolve[{eqns, cond},f,{t,0,1200}][[1]];>> a=sol[[1, Something, 2]]>> b=sol[[1, Something+1, 2]]>>>> Plot[{a[t],b[t]}],{t,0,1200}],>>>> and that was it. However I don't understand this. Was the problem the>> "size" and "amount" of interpolated functions?>>>>> --> DrMajorBob@yahoo.com>
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