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maple plot directional field without detools

This is a homework problem. I am to plot the directional field of the ode y' = x*y/2 using for loops and or procs. I have the following code:

X := [seq(.1*x, x = -20 .. 20)]; 
Y := [seq(y, y = -2 .. 2, .1)]; 
P := Array([seq(0, x = 0 .. 41^2-1)]);
with(plots); 
for k to 41 do for j to 41 do
slope := (1/2)*X[k]*Y[j]; 
Xp := [X[k], X[k]+.1]; Yp := [Y[j], Y[j]+0.1*slope]; 
P[41*(k-1)+j] := plot(Xp, Yp) end do end do;
display(P);

and get something really awful looking which isn't right.I understand it a lot of plots and would be easier to use detools but as stated it's for homework. I get something like this: https://i.sstatic.net/UArMP.png

Solution

  • You can see why the display(P) looks wrong if you do display(P[1..2]) - it is a "window of plot windows".

    You need to tell Maple that P is not one object but that the display should be of 1681 plots, e.g. with the sequence functional.

    display(seq(P[i], i = 1..numelems(P)));

    Directional field