MATLAB: No Arrows showing in plot When using quiver

MATLABplottingquiver

I am new to Matlab. Trying to use quiver to plot a velocity field. This is my code that gets to the plot but doesn't show any arrows.

[x,y] = meshgrid(0:0.2:5,0:0.2:5);

u = 2./x;

v = 2.*y./(x.^2);

figure

quiver(x,y,u,v)

Best Answer

As the grid starts from 0 and you have used this zero in the reciprocal to get (u,v) you will get inf in the u,v.; quiver uses maximum value of u and v to scale the arrows and plot. Try to repalce inf with some other value or avoid zero.

[x,y] = meshgrid(1:0.2:5,1:0.2:5);
u = 2./x;
v = 2.*y./(x.^2);
figure
quiver(x,y,u,v,1,'r')

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Quiver_tri arrow length

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[x,y] = meshgrid(0:0.5:2,0:0.5:2);
u = cos(x).*y;
v = sin(x).*y;
figure
quiver(x,y,u,v)

[x,y] = meshgrid(0:0.2:2,0:0.2:2);
u = cos(x).*y;
v = sin(x).*y;
figure
quiver(x,y,u,v)

MATLAB: Quiver plotting arrow length

Two things:

(1) It looks like you swapped the u and v arguments compared to how you actually want them, so I think you actually want

quiver(x,y,u,v)

(2) There is an automatic scaling that occurs to the arrow (which is described in the documentation). You can turn off that scaling:

quiver(x,y,u,v,0)

I believe that will result in the plot you expect.

Best Answer

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