Using bar3 and color coordinating the height depending on the value

Hello, I am trying to adjust the following code from the documentation to create a 3D barchart and have the height colored depending on the value

% From documentation
Z = magic(5);
b = bar3(Z);
colorbar
for k = 1:length(b)
    zdata = b(k).ZData;
    b(k).CData = zdata;
    b(k).FaceColor = 'interp';
end

This is my data, (Im just plotting one column, column 2)

data =

          1.00         44.48          8.20
          2.00         68.53        140.26
          3.00       3628.97        843.39

and the code Im using.

b1=bar3(data(:,2));
for k = 1:length(b1)
    zdata = b1(k).ZData;
    b1(k).CData = zdata;
    b1(k).FaceColor = 'interp';
end

and this is what I get

and if I check the ZData:

b1.ZData

I get

Zdata =

           NaN             0             0           NaN
             0         44.48         44.48             0
             0         44.48         44.48             0
           NaN             0             0           NaN
           NaN             0             0           NaN
           NaN           NaN           NaN           NaN
           NaN             0             0           NaN
             0         68.53         68.53             0
             0         68.53         68.53             0
           NaN             0             0           NaN
           NaN             0             0           NaN
           NaN           NaN           NaN           NaN
           NaN             0             0           NaN
             0       3628.97       3628.97             0
             0       3628.97       3628.97             0
           NaN             0             0           NaN
           NaN             0             0           NaN
           NaN           NaN           NaN           NaN
           

what are all the extra rows and columns? They seem to be messing up what I want to do

Answer 1

[dpb]

They're all the faces color vertices data -- it's a convolved mess to fiddle with manually, fer shure, good buddy! :(

Your code is ok, the problem is the scaling of the three bars is so disparate the linear scaling isn't effective. Try

   b1(k).CData = log10(zdata);

and you'll at least see some differences...not sure the best generic solution for such a case, but that's the root cause problem.

[Jason]

Thank you for this. But why does the Zdata contain duplicates and extra rows and columns?

[Jason]

Sorry i didnt read properly, they are all the vertices

[Jason]

Actually, its still not quite right.

I wanted the vertical walls to also change colour gradually, at the moment its just the tops of the bars.

I used this as my data.

data=[33;44;120;66;17]
b1=bar3(data);
for k = 1:length(b1)
    zdata = b1(k).ZData;
    b1(k).CData = log10(zdata);
    b1(k).FaceColor = 'interp';
end

[dpb]

That has to do with only using the one column/row -- and I'm not sure otomh just what would need to fixup to produce the effect, sorry.

Try changing you data vector to

data=[data data];

and the same code (excepting take the log10 scaling back out) and you'll see the shading come back.

I remember digging into the CData stuff pretty throughly a couple years ago and there being a thread/Answer on the subject but I'd have no way to find it quickly at the moment, unfortunately.