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Question: How to plot vector fields?

Question:How to plot vector fields?

Dkunb 70 Maple 2021
ode differential-equations deplot plotting
March 08 2023
0
> 

restart;
> 

with(Physics):with(plots):with(DETools):
> 

sys := {diff(r(t),t)=p(t)/m,
diff(p(t),t)=l^2/(m*r(t)^3)-n*k*r(t)^(n-1),
diff(phi(t),t)=l/(m*r(t)^2)};

{diff(p(t), t) = l^2/(m*r(t)^3)-n*k*r(t)^(n-1), diff(phi(t), t) = l/(m*r(t)^2), diff(r(t), t) = p(t)/m}

 (1)
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sys1:=subs({n=1,k=1},sys);

{diff(p(t), t) = l^2/(m*r(t)^3)-1, diff(phi(t), t) = l/(m*r(t)^2), diff(r(t), t) = p(t)/m}

 (2)
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conv:=plottools:-transform((a,b)->[a*cos(b),a*sin(b)]):
> 

p1:=DEplot(sys1,[r(t),phi(t)],t=0..30,r=0..10,phi=0..2*Pi,stepsize=0.01);

Error, (in DEtools/DEplot) system must have same number of dependent variables as DE's.

  
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plots:-display([conv(p1)],axiscoordinates=polar);

Error, (in conv) invalid argument

  
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Could you help how to fix the code?

Download DEplot_v1.mw
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