question ,,thankx!!!
- To: mathgroup at smc.vnet.net
- Subject: [mg70681] question ,,thankx!!!
- From: "walkon" <fsun81 at mail.ru>
- Date: Mon, 23 Oct 2006 02:49:59 -0400 (EDT)
hello to everyone! here question is: input: r[t_] := 0 /; (t > 0) && (t < 100) r[t_] := 10 /; (t > 100) && (t < 110) r[t_] := 2.5 /; (t > 110) && (t < 200) r[t_] := 0 /; (t > 200) && (t < 400) sol = NDSolve[{b'[t] == 30a'[t], c'[t] == 10a[t](100 - c[t]) -0.3c[t], d'[t] ==400a[t], a'[t] + b'[t] + c'[t] + d'[t] == r[t], a[0] == 0, b[0] == 0, c[0] == 0, d[0] == 0}, {a[t], b[t], c[t], d[t]}, {t, 0, 400}] Plot[({a[t], b[t], c[t], d[t]} /. sol[[1]] // Evaluate), {t, 0,400}, PlotRange -> All, Frame -> True] who can tell me what 's wrong with the programming? and if I input a certain r[t] value like: input: sol = NDSolve[{b'[t] == 30a'[t], c'[t] == 10a[t](100 - c[t]) -0.3c[t], d'[t] ==400a[t], a'[t] + b'[t] + c'[t] + d'[t] == 0, a[0] == 10, b[0] == 0, c[0] == 0, d[0] == 0}, {a[t], b[t], c[t], d[t]}, {t, 0, 100}] Plot[({a[t], b[t], c[t], d[t]} /. sol[[1]] // Evaluate), {t, 0,100}, PlotRange -> All, Frame -> True] output: [Graphic] It works well! so,,whether the programming can only be seperately resolved or not? the most important is that I need to get the numerical value of a[t],b[t],c[t],d[t] at each time point(0-400),but how to list them from the result of NDSolve??even I can show the picture. thank you very much!!!