Re: How to change time stepsize for Integration

*To*: mathgroup at smc.vnet.net*Subject*: [mg33982] Re: How to change time stepsize for Integration*From*: "Allan Hayes" <hay at haystack.demon.co.uk>*Date*: Thu, 25 Apr 2002 03:00:00 -0400 (EDT)*References*: <aa5gkf$c09$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Winston, NDSolve has the option MaxStepSize Plot has the option PlotPoints, which determines the initial sample points Table has the syntax Table[expr, {x,a, b, stepsize}] (*but to reach b, stepsize must be (b-a)/n*) -- Allan --------------------- Allan Hayes Mathematica Training and Consulting Leicester UK www.haystack.demon.co.uk hay at haystack.demon.co.uk Voice: +44 (0)116 271 4198 Fax: +44 (0)870 164 0565 "Winston Garira" <uceswga at ucl.ac.uk> wrote in message news:aa5gkf$c09$1 at smc.vnet.net... > Hi! > > Can anyone help me on this one: > > > Pends[init_, time_, {c_, w_, p_}] := > Module[{}, > pend = NDSolve[{x''[t] + c x'[t] + (1 + p Cos[w t])Sin[x[t]] == 0, > x[0] == init[[1]], x'[0] == init[[2]]}, {x}, {t, 0, time}, > MaxSteps -> 200000]; > xd[t_] := x[t] /. pend[[1]]; > xdd[t_] := x'[t] /. pend[[1]];]; > c = 0.1; w = 0.30; p = 1.1; > > Pends[{1.37, 0}, 5000, {c, w, p}]; > plt = Plot[{t, xd[t], xdd[t]}, {t, 0, 500}]; > > I want to reduce the time stepsize > in my numerical integration with mathematica. Each time > I try to get coordinates generated from the command > Plot[ ......, {t, tmin, tmax}]; or > Table[......, {t, tmin, tmax}]; > > I always notice that in all these case time stepsize = 1. > Is there anyway I can reduce the the timestep to say, > time stepsize =0.001 in the above numerical integration using > NDsolve. > > > Thanks in advance > > Winston > >