Scatter3, insert dashed line downwards, and sideways

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.

Answer 1

[Giovanni Mottola]

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):

[Joel]

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]

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]

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]

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]

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!