MATLAB: Different colours for arrows in quiver plot

different colorsquivervector

Hi Everyone,
I want to plot arrows with different magnitude and directions in different colors.The code need to calculate the angle of the each vector and fit them in the colormap.
This is what I have wrote but is there anyone that can help me to find the example or any other command or function in matlab that can plot this for me?
for i=1:40
     structure(i,:,:)=rombohedral((i-1)*338+1:i*338,:);
   
     X=structure(i,:,4);
     Y=structure(i,:,5);
     Z=structure(i,:,6);
     U=structure(i,:,7);
     V=structure(i,:,8);
     W=structure(i,:,9);
     C=zeros(338,3);
     C(1:300,1)=1;
     C(300:end,2)=1;
     figure(i)
     figure(i)
     title('2D')
     t=num2str(i);
     xlabel([t,' ps'])
     hold on
    
    for j=1:338
        if (U(j)>0)
           quiver(X(j),Y(j),U(j),W(j),'color',[1 0 0])
        elseif (U(j)<0)
           quiver(X(j),Y(j),U(j),W(j),'color',[0 1 1])
        elseif (V(j)>0)
          quiver(X(j),Y(j),W(j),V(j),'color',[0 1 0])
        elseif (V(j)<0)
          quiver(X(j),Y(j),W(j),V(j),'color',[1 0 1])
        end
    end
   
 
end

Best Answer

Create a circular colormap: 
cmap = colormap(hsv(360));
In the loop: compute the angle and an index into the colormap from the angle
 alpha = atan2(W(j), U(j)); % or V(j), W(j) depending on your elseif clause
Convert angle to index
 idx = ceil(rad2deg(alpha));
 if alpha < 1 % negative indices and 0 are invalid 
     idx = idx + 360;
 end
 set(h, 'Color', cmap(idx,:)) % before, change each quiver command to h = quiver(...)
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