Plotting portion of a color coded scatter plot using a for loop

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AN 2023-4-11

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https://ww2.mathworks.cn/matlabcentral/answers/1945499-plotting-portion-of-a-color-coded-scatter-plot-using-a-for-loop

评论： AN 2023-4-11

Hi all,

I have created a value-based color coded 4-dimensional scatter plot of a heart (color coded based on activation times corresponding to each xyz point). The xyz coordinates are designated by vectors (x_points, etc...) and the corresponding colors to each xyz point are defined in an nx3 array called rgb_time. I have divided the scatter plot into cubic voxels using discretize, and am attempting to create scatter plots of individual voxels displaying the same color code of the original scatterplot. I am using the following code to loop through the points and determine the ones within the voxel of interest before plotting them:

i_max = 6; %arbitrary value
%graph only the cube containing the most colors (area of interest)
figure() 
hold on
for i = 1:size(rgb_time)
    if voxelIDs(i) == i_max 
        scatter3(x_points(i),y_points(i),z_points(i),20,rgb_time(i),'filled')
        xlabel('x');ylabel('y');zlabel('z');title('voxel containing isochronal crowding');
        str = 'early - red - orange - yellow - green - cyan - blue - purple - pink - late';
    end
end

For some reason, however, the resultant voxel plot has distorted colors that are not the same as those displayed on the original scatter plot. Could anyone have an idea as to why this is? I have tried moving the hold on statement to various locations to no avail. Thank you!

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AN 2023-4-11

I have attached examples of the original scatter plot with the desired colored regions, as well as a subset/voxel scatter plot with distorted colors.

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Answer 1

Ran Yang 2023-4-11

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https://ww2.mathworks.cn/matlabcentral/answers/1945499-plotting-portion-of-a-color-coded-scatter-plot-using-a-for-loop#answer_1213929

编辑：Ran Yang 2023-4-11

rgb_time is a Nx3 array, so you need to call all 3 columns using rgb_time(i, :) to get the color for each voxel. (Right now you're only getting column 1).