How to plot color indication on the points in 2D and 3D

I have a set of data looks like this

X Y  Z  Intensity

-10  -10  15  100

-10  -10  16  200

-9  -10  15  150

-9  -10  16  130

-8  -10  15  110

-8  -10  16  117

-10  -9  15  210

-10  -9  16  189

-9  -9  15  234

-9  -9  16  156

-8  -9  15  175

-8  -9  16  183

-10  -8  15  216

-10  -8  16  260

-9  -8  15  144

-9  -8  16  190

-8  -8  15  128

-8  -8  16  219

The actual data file is much bigger. In the X-Y plane, I was trying to plot the color indication with the given Intensity for a fixed point in Z.

And is it possible that i cant plot a 3D view with the color indications using the current fields of data that I've.

I had tried to looked up on colormap, surf functions, but I don't know how to use them correctly.

Thanks

Answer 1

[Walter Roberson]

pointsize = 20;
scatter3(x(:), y(:), z(:), pointsize, intensity(:));

You can take subsets of the data for particular z, if you want. For example

idx = z == 16;   %watch out for floating point comparisons if the values are not integers!
scatter3(x(idx), y(idx), z(idx), pointsize, intensity(idx));

[zhenhan weng]

thank you for your response Walter, may I ask if it is possible to display the plots like the following 2 example image?

Image 3D:

Image 2D

Or my data points has not enough information to produce such plots?

[Walter Roberson]

gridsize = 36;  %adjust as needed
constant_z = 15;  %adjust as needed

minvals = min(XYZI, 1);
maxvals = max(XYZI, 1);

[X,Y,Z] = meshgrid( linspace(minvals(1),maxvals(1),gridsize), linspace(minvals(2),maxvals(2),gridsize), constant_z);
Vq = griddata(XYZI(:,1), XYZI(:,2), XYZI(:,3), XYZI(:,4), X, Y, Z);

surf(X, Y, Z, Vq);

and you can look at the same thing after doing

view([0 90])

You might notice that the 3D image is "flat". You wrote earlier "I was trying to plot the color indication with the given Intensity for a fixed point in Z." Fixed point in Z implies flat.

If you remove the restriction about "fixed point in Z" then to get a 3D graph you need to ask whether there is only one Z for each unique (X,Y) pair, because if so then the single Z can be used as the height. But your data is not unique in Z, only in (X,Y,Z). We therefore do not know which of the multiple Z to pick. We can invent solutions such as picking the Z that corresponds to the maximum intensity.

It looks as if possibly your data forms a cuboid, that you have a series of X, Y, and Z, and that you have intensity data for each combination of those. If that is the case then you should be considering slice() or isosurface() or considering voxel viewing

[zhenhan weng]

thank you very much for your answer. Cheers