Hi！  everyone！  Day day study    Day day up！

Thank you!  Here what i mostly want is the phaseplan of (x(t),y(t)) of this ODE system.  Is ther any method?  Thank you again!

Hi！  everyone！  Day day study    Day day up！

Thank you very much! I already know this. But can you tell me how to get the phaseplan of (x(t),y(t))?I do this withscene(x(t),y(t)),but the graph i get do not has arrows that i really want!  I will greatly appreciate your help!

Hi！  everyone！  Day day study    Day day up！

I know this, but the example in maplehelp has only two functionsx(t)and y(t),when here I have four eqs,and the result is "Error, (in DEtools/DEplot) system must have same number of dependent variables as DE's."

Can anyone find why? Thank you very much!

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Yes, I am too careless. The second point you said is the right source of the puzzling big number. Thank you very much!

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Thank you and I will have a try!

Thank you very much!   this is very helpful !  Thank you again!

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Yes, I get the above graph,but when  I chage 1 to 0.1 in the “range=”

> PDE := diff(u(x,t),t)+diff(u(x,t),x)=0;  IBC := {u(x,0)=x,u(0,t)=0};

pds := pdsolve(PDE,IBC,numeric,time=t,range=0 .. 1);

pds:-plot3d(t = 0 .. .1, x = 0 .. 1, axes = boxed, orientation = [-110, 60], color = [0, 0, u]);
  and the result is   (in the file)  many thanks!View 10762_two different graphs.mw on MapleNet or Download 10762_two different graphs.mw
View file details

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Hello!  What I mean is that any procedure you write in maple 12 can not be opened correctly by maple 10. And the form I save is Maple 12 Worksheet File!  many thanks

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Hello! I changed the value to 0..1 and the result still give 4500！ I do not  know why! Perhaps my computer is going wrong!

In addition,could you explain that  “the "range" should be for the variable that is not "time"”?

Hi！  everyone！  Day day study    Day day up！

Thank you very much and the above procedure goes very well!  this question puzzled me for  several days!  Good answer and good day!