My question is in regards to the events feature in dsolve numeric.

At a particular event time, I was wondering if it is possible to call a previous moment, that is something like

eq:={ diff(y(t),t) = y(t) };

ic:={ y(0) = 2 };

de:=dsolve( eq union ic, numeric, events=[[ t =5, [ y(t) = y( t - 2 ) ]]],range=0..10);


If it is possible to "globaly" declare previous steps of the dsolve, I believe that the above de would work. However,...

The problem i have is this, the plot that i am suppose to recieve is one that looks like the 'pointplot3d' below, yet i recieve something which doesn't. Any suggestions as to how to circumvent this? with(plots):Digits:=15: > Omega[0,1]:=.825352549049169: plot3d(MathieuCE(0,Omega[0,1],r*I)*MathieuCE(0,Omega[0,1],theta),theta=0..2*Pi,r=0..1,coords=ellcylindrical,axes=FRAMED); points1:={seq(seq([T/100,2*Pi*S/100,MathieuCE(0,Omega[0,1],2*Pi*S/100)*MathieuCE(0,Omega[0,1],I*T/100)],T=1..100), S=1..100)}: pointplot3d(points1,coords=ellcylindrical, axes=FRAMED, color=red, style=wireframe);

I was wondering if some one had the knowledge as to why the plot3d command will not work for the dirichlet elliptical wave equation, at fixed time t, yet maple is able to evaluate this function at specific values for theta and r. (the coord system for the 3d plot should work with "ellcylindrical" but does not)

the modes of the function look like (for Cosine-Elliptic)

MathieuCE(j,q,theta)*MathieuCE(j,q,I*r)*cos(lambda*t)

j=0, 1, 2...n where q is a 'zero' value of MathieuCE(j,q,I*1) 0<theta<2*Pi, 0<r<1, t>=0

the error stated is "Plotting error, MESH must be a list of lists of vertices, or an hfarray"