how to limit arrow length in 3D quiver plot?

I have a vector field with a large dynamic range; I would like to set a high threshold on vector magnitudes being displayed.

logarithmic scale would also help.

Answer 1

[A]

here is what works:

       Ln = sqrt(U.^2 + V.^2 +W.^2);  
       Maxlen=100;

       U(Ln>Maxlen)=U(Ln>Maxlen)./Ln(Ln>Maxlen).*Maxlen;
       V(Ln>Maxlen)=V(Ln>Maxlen)./Ln(Ln>Maxlen).*Maxlen;
       W(Ln>Maxlen)=W(Ln>Maxlen)./Ln(Ln>Maxlen).*Maxlen;
       quiver3(X,Y,Z,U,V,W)

Answer 2

[Matt Kindig]

For your situation, I would specify the length of the arrows directly, rather than letting Matlab perform the Auto-scaling of the vectors. This would allow you to specify upper bounds on the lengths, log scaling, or whatever else you prefer. Something like this:

% X,Y,Z are the origins of your vectors
% U,V,W are the directions of your vectors
Ln = sqrt(U.^2 + V.^2 +W.^2);  
U = U./Ln; V = V./Ln; W = W./Ln;  %normalize vectors
Maxlen = 100;   %set this based on your preference
U = U*Maxlen;   %this will set 'Maxlen' as the max length 
V = V*Maxlen;  
W = W*Maxlen;

%or for log scaling, 
U = Maxlen*log(U);  %or similar
V = Maxlen*log(V);
U = 

hq = quiver3( X, Y, Z,

[A]

wouldn't this set all vectors to the same length?

[Matt Kindig]

Ah, yes it would. My apologies. You should normalize by the maximum of Ln, rather than Ln itself.

Answer 3

[Sean de Wolski]

Couldn't you just takle the log or log10 f the u/v/w components?

2-d example:

[xx yy] = meshgrid(1:5);
u = (rand(5)+1).^(rand(5)*10);
v = (rand(5)+1).^(rand(5)*10);

quiver(xx(:),yy(:),log10(u(:)),log10(v(:)))

More per comments Let's not give up on this yet!

[xx yy] = meshgrid(1:5);
u = (rand(5)+1).^(rand(5)*10)*sign(randn(5));
v = (rand(5)+1).^(rand(5)*10)*sign(randn(5));

quiver(xx(:),yy(:),sign(u(:)).*log10(abs(u(:))),sign(u(:)).*log10(abs(v(:))))

[A]

components could be negative; log would not work

[Sean de Wolski]

please see update.