How to group and then 3D plot a column in a matrix?

Dear All,

I have matrix M that is 2500x4 like so (I put in the headings myself):

    Color     X           Y           Z
    42        1.006431    1.144329    92.1
    43        1.006436    1.122343    61.1
    42        1.006553    1.023647    54.1
    33        1.006755    1.754235    73.2
    47        1.006043    1.234565    87.6
    39        1.006324    1.622433    99.5
    ...       ...         ...         ...

I would like to plot the Color column as a 3D plot with X Y and Z as my coordinate system. Each point will vary according to the value of Color. However, since there are many variables, it may be smarter to put all the common X, Y, Z values into groups and averaging the Color in each group. X and Y can be 5 significant figures each and Z can be 2 significant figures. For example, at (1.0064,1.1443,92), the average color will be some value around 42. If you are confused please let me know. Thank you for your time.

Answer 1

[Carl]

You can use the scatter3 function and specify the color for each one of your points. See the quick example below:

c = zeros(6,3);
data = [(1:6)', (1:6)', rand(6,1)];
% red if z greater than 0.5
c(data(:,3) > 0.5, 1) = 1;
% blue if z less than or equal to 0.5
c(data(:,3) <= 0.5, 3) = 1;
scatter3(data(:,1),data(:,2),data(:,3),[],c,'filled')

See the documentation for more details on using the scatter3 function:

http://www.mathworks.com/help/matlab/ref/scatter3.html

Specifically, you can supply the value of c as a "three-column matrix of RGB triplets" as shown above, or define your own colormap and index into it.