Question: arrows do not appear in system of DE

Hi,

Happy new year.

I have a problem, if it is possible please guide me.

I want to add "arrows=small/curve/...." (i.e. vector fields) to the following maple's example, but unfortanutley it does not work (see the green code and run it ....).

It is not important to me that I use phaseportrait or DEplot or dfieldplot, I just want to show arrows in any "scene" that I choose.

restart;

with(plots);
with(DEtools);
with(VectorCalculus);
BasisFormat(false);

DEplot({D(w)(t) = x(t) - w(t)*z(t), D(x)(t) = y(t) + z(t), D(y)(t) = -x(t) - y(t) + w(t), D(z)(t) = x(t) + y(t) - z(t)}, [x(t), y(t), z(t), w(t)], t = 0 .. 10, [[x(0) = 0, z(0) = 0.25, y(0) = 0.5, w(0) = 0.165]], scene = [z(t), w(t)], numsteps = 101, axes = BOXED, linestyle = dashdot, method = rkf45, startinit = true, maxfun = 5000, xtickmarks = 10, arrows = medium);

Indeed I want to get something like this:

DEplot([diff(x(t), t) = -0.5*x(t)*y(t), diff(y(t), t) = 0.5*x(t)*y(t) - 0.15*y(t)], [x(t), y(t)], t = 0 .. 40, x = 0 .. 1, y = 0 .. 0.6, [[x(0) = 0.99, y(0) = 0.01]], arrows = medium);

In this plot, we can observe arrows (vector fields), but in the first example, I cannot to handle it.

Thanks in advance.