I can't draw the vector field

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윤형
윤형 on 4 Jun 2023
Answered: the cyclist on 4 Jun 2023
[x, y] = meshgrid(-0.9:0.3:0.9, -0.9:0.3:0.9);
R1 = (x.^2 + y.^2).^.5;
V = 1./R1;
figure(1)
surf(x, y, V)
view(-37.5, 20)
figure(2)
contour(x, y, V, 5)
hold on
axis square
[u, v] = gradient(V, 0.2);
quiver(x, y, -u, -v, 1.5)
axis equal
I can't draw the vector field. What's the problem

Answers (2)

Simon Chan
Simon Chan on 4 Jun 2023
The spacing used in function gradient is 0.2, but the spacing in your data is 0.3 and hence it give you an error. Try using same spacing.

the cyclist
the cyclist on 4 Jun 2023
The problem is the Inf values in u and v. Removing them:
[x, y] = meshgrid(-0.9:0.3:0.9, -0.9:0.3:0.9);
R1 = (x.^2 + y.^2).^.5;
V = 1./R1;
figure(1)
surf(x, y, V)
view(-37.5, 20)
figure
contour(x, y, V, 5)
hold on
axis square
[u, v] = gradient(V, 0.2);
u(isinf(u)) = NaN;
v(isinf(v)) = NaN;
quiver(x, y, -u, -v,1.5)
axis equal

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