Update on bug in Maple 9.5 plot3d

Discussion in 'Maple' started by John Starrett, Nov 28, 2004.

  1. I am plotting a solution for a known chaotic system of three first order
    ODEs, along with their isosurfaces, which are obtained by setting the
    derivative equal to zero for each of the three equations. The change in
    the solution in the x, y and z direction should be zero through the
    surfaces Isurf1, Isurf2 and Isurf3 respectively. When plotted, this
    displays (usually) incorrectly:

    DE1:=diff(x(t),t)=-z(t);
    DE2:=diff(y(t),t)=x(t)-y(t);
    DE3:=diff(z(t),t)=alpha*x(t)+y(t)^2+beta*z(t);

    DE1a:=subs(alpha=3.1,beta=0.5,DE1);
    DE2a:=subs(alpha=3.1,beta=0.5,DE2);
    DE3a:=subs(alpha=3.1,beta=0.5,DE3);

    SPROTT:=DEplot3d({DE1a,DE2a,DE3a},{x(t),y(t),z(t)},
    t=0..300,stepsize=.05,[[x(0)=.1,y(0)=.1,z(0)=.1]],linecolor=black,thickness=1):

    Isurf1:=implicitplot3d({z=0}, x=-9..9, y=-9..9, z=-9..9,
    axes=boxed,color=blue):
    Isurf2:=implicitplot3d({x-y}, x=-9..9, y=-9..9,
    z=-9..9,axes=boxed,color=yellow):
    Isurf3:=implicitplot3d({z=-6.2*x-2*y^2}, x=-9..9, y=-9..9, z=-9..9,
    axes=boxed,color=red):

    display(Isurf1,Isurf2,Isurf3,SPROTT);


    However, when the variables y and z are interchanged in the definitions
    of the ODEs,

    DE1:=diff(x(t),t)=-y(t);
    DE2:=diff(z(t),t)=x(t)-z(t);
    DE3:=diff(y(t),t)=alpha*x(t)+z(t)^2+beta*y(t);

    the plot displays correctly (usually).

    What is especially troubling is that sometimes it plots correctly and
    sometimes it doesn't. I have done this literally dozens of times and can
    find no pattern or clue as to when I will need to interchange the
    variables y and z to get this to plot properly.
     
    John Starrett, Nov 28, 2004
    #1
    1. Advertisements

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.