Histograms from point cloud

Hello,

Basically, I have 3D coordinates points (xyzPoints) and I want to display 3 histograms of x, y and z coordinates values in order to visualize the density of data cloud.

xyzPoints = reconstructScene(disparityMap, stereoParamsTEST);
xyzPoints = xyzPoints./1000;
ptCloud = pointCloud(xyzPoints);
figure(4);
pcshow(ptCloud);
title('Point cloud');

How do I create variables for x, y and z coordinates values to do this :

subplot(2,2,1);
hist(x);
subplot(2,2,2);
hist(y);
subplot(2,2,3);
hist(z);

Thanks

Answer 1

[Rik]

It looks like you can use the columns from xyzPoints, because they seem to store the coordinates. Otherwise you could also use the location property of your point cloud object.

[Théodore Keller]

It seems I can't because 'x' variable doesn't exist. The size of xyzPoints is 2019x4063x3.

What is the location proprety of the point cloud ?

[Rik]

You need to save the data to that variable first. The property I was referring to can be found in the documentation for the pointCloud function.

But as Steven points out: you can simply do something like this.

xyzPoints = reconstructScene(disparityMap, stereoParamsTEST);
xyzPoints = xyzPoints./1000;

figure(1),clf(1)%create a clean window (bring to focus and clear if it already exists)
for dim=1:3
    subplot(2,2,dim);
    temp=xyzPoints(:,:,dim);
    hist(temp(:));
    
    title(char('x'-1+dim))%use a trick to map {1 2 3} to {'x' 'y' 'z'}
end

[Théodore Keller]

Thank you !

Answer 2

[Steven Lord]

You said in your comment to Rik's answer that xyzPoints is size [2019 4063 3]. I assume therefore that the x data is the first page of that data xyzPoints(:, :, 1), the y data is the second page xyzPoints(:, :, 2), and the z data is the third page xyzPoints(:, :, 3)? If so, call histogram on each of those pages of data.

Alternately you could plot them using scatter3 or perhaps make a trio of heatmap plots: one for x versus y, one for x versus z, and one for y versus z.

[Théodore Keller]

Thank you !