Help with the following error with quiver

I am getting the above error using the function quiver for vector field

x = -4e-7:0.1e-12:4e-7;
y = -4e-7:0.1e-12:4e-7;
[X,Y] = meshgrid(x,y);
HX = (atan(((g/2 + X)./Y);
HY1 = (cos((g/2 + X).^2 + (Y).^2/(g/2 - X).^2 + (Y).^2));
H = sqrt(HY1.^2 + HX.^2);
quiver(H,X,Y);

[Voss]

I believe it's likely that there's a missing period in your expression for HY1. Please see below.

g = 10;
x = -4e-7:0.1e-7:4e-7;
y = -4e-7:0.1e-7:4e-7;
[X,Y] = meshgrid(x,y);
HX = (1/pi)*(atan(((g/2 + X)./Y) + atan((g/2 - X)./Y)));

HY1 = (-1/2*pi)*(log((g/2 + X).^2 + (Y).^2./(g/2 - X).^2 + (Y).^2));
%    You probably should have this . here ^

H = sqrt(HY1.^2 + HX.^2);
quiver(X,Y,HX,HY1); % ?

[Walter Roberson]

You need to resolve H into horizontal and vertical components, and pass quiver(X, Y, horizontal, vertical)

Your current H looks like a pure magnitude.

[Rena Berman]

(Answers Dev) Restored edit

[Stephen23]

https://web.archive.org/web/20220524062504/https://www.mathworks.com/matlabcentral/answers/1679129-help-with-the-following-error-with-quiver

[Rik]

Editing away your question is very rude, please don't do it again.

Answer 1

[Sam Chak]

Hi @Amy Topaz

If g is assumed as the gravity, then the "Region of Repulsion" is found here. Solving the simultaneous equations and give two saddle points somewhere around and region. Check it out.

[X, Y] = meshgrid(-7:4/14:-3, -2:4/14:2);
g = 10;
U = (1/pi)*(atan(((g/2 + X)./Y) + atan((g/2 - X)./Y)));
V = (-1/2*pi)*(log((g/2 + X).^2 + (Y).^2./(g/2 - X).^2 + (Y).^2));
quiver(X, Y, U, V, 1.5)
axis square
axis([-7.5 -2.5 -2.5 2.5])

[Sam Chak]

Hi @Amy Topaz

Are you looking for 3-D vector field like this?

[X, Y, Z] = meshgrid(-7:4/14:-3, -2:4/14:2, 0:4/14:4);
g = 10;
U = (1/pi)*(atan(((g/2 + X)./Y) + atan((g/2 - X)./Y)));
V = (-1/2*pi)*(log((g/2 + X).^2 + (Y).^2./(g/2 - X).^2 + (Y).^2));
H = sqrt(U.^2 + V.^2);
h = quiver3(X, Y, Z, U, V, H);
set(h, 'maxheadsize', 1.5);

Answer 2

[Walter Roberson]

quiver has a few calling sequences:

• quiver(x, y, u, v)
• quiver(u, v)
• either of those followed by a scale factor
• any of the above proceeded by an axes handle

You are using three parameters, so you are either using axes, u, v or else u, v, scale. But the first parameter is not an axes so you are using u,v, scale

Did you possibly intend to use quiver3?