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Joel on 6 Oct 2016
Commented: Joel on 6 Oct 2016
Accepted Answer: Giovanni Mottola
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I want to show my data in a scatter3 plot.
However, the way the data is shown, it is not very clear where exactly on the 3 axis the data points are.
An example,
figure;
x = 0.9914;
y = 0.0390;
z = 20
scatter3(x,y,z,'filled')
view(-30,10)
What I would like to do is to draw a dashed line straight downwards from the point, so that it is clearer where the point is on the XY plane. Also, I would like to draw a dashed line from the point to the Z axis, so that it is clear where the point is on the Z axis plane.
If this turns out to be too messy I will look at a way to write the XYZ values for each point just above each point.
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Accepted Answer
Giovanni Mottola on 6 Oct 2016
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Open in MATLAB Online
Here I assumed x, y, z are vectors of length "len".
To draw a line joining each scatter point to the horizontal plane use:
hold on
for i=1:len
plot3([x(i), x(i)], [y(i), y(i)], [0, z(i)], 'b--')
end
To draw a line joining each scatter point to the vertical axis use:
for i=1:len
plot3([0, x(i)], [0, y(i)], [z(i), z(i)], 'r--')
end
Final result for len=5 (random points):
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Joel on 6 Oct 2016
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https://uk.mathworks.com/matlabcentral/answers/306041-scatter3-insert-dashed-line-downwards-and-sideways#comment_396423
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Thanks!
The dashed line downwards works just like I want it to!
However, something is off with the dashed line for the Z axis. It is not dashed in a 90 degree angle, i.e. it shows the wrong z axis value. I have not yet figured out why this is. I tried setting the Z value to the maximum to see, and the dashed line is not right. COuld it be because in ym example the 3 axis are not of the same length (same min/max)?
This is a minimum working example of my code,
figure;
x = 0.9914;
y = 0.0390;
z = 2
scatter3(x,y,z,'filled')
ylim([-2, 2])
xlim([-2 2])
zlim([0 2])
hold on
plot3([x, x], [y, y], [0, z], 'b--')
plot3([0, x], [0, y], [z, z], 'r--')
view(-30,10)
Giovanni Mottola on 6 Oct 2016
Direct link to this comment
https://uk.mathworks.com/matlabcentral/answers/306041-scatter3-insert-dashed-line-downwards-and-sideways#comment_396457
I tried running your code and I'm not sure what the problem is. My results are below. Are you sure it's not a matter of perspective? Could you try to set the same limits for x, y and z axes (with xlim etc.)?
Joel on 6 Oct 2016
Direct link to this comment
https://uk.mathworks.com/matlabcentral/answers/306041-scatter3-insert-dashed-line-downwards-and-sideways#comment_396471
Very strange that your figure looks perfect. Hm. As you can see in the image, it is clear that the red dashed line does not go to the value 2 on the Z axis.
I really do not have any good guess as to why this could be at the moment.
Thank you for your help thus far. I appreciate it!
Giovanni Mottola on 6 Oct 2016
Direct link to this comment
https://uk.mathworks.com/matlabcentral/answers/306041-scatter3-insert-dashed-line-downwards-and-sideways#comment_396486
Open in MATLAB Online
Try:
view([0, 0])
ylim([0 2.2])
xlim([0 2.2])
zlim([0 2.2])
And
view([90, 0])
ylim([0 2.2])
xlim([0 2.2])
zlim([0 2.2])
Joel on 6 Oct 2016
Direct link to this comment
https://uk.mathworks.com/matlabcentral/answers/306041-scatter3-insert-dashed-line-downwards-and-sideways#comment_396531
Thanks Giovanni!
You are/were indeed right that it is an issue of perspective.
Still if I would like to show this plot to someone it is very misleading. By looking at the figure I posted one does not think the Z value is 2.
I tried some other perspectives and I noticed that when the first variable of view is negative I get plot where it seems like Z is not 2. If I change it to positive, then it looks as I expect it to!
Thank you very much for your help!
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