How do I colour different segments of a bar within a bar graph different colours (red or green) depending on if data has reached a threshold value

Im trying to get a bar graph with force on y axis and weight on x axis. However, I want each bar to have segments of red and green depending on whether a threshold value has been met for positional data that was also recorded. How would this be done

% Create bar graph
figure;
hold on;
for i = 1:length(weights)
    weight = weights{i};
    force_vals = force_data{i};
    zcom_vals = zcom_data{i};
    for j = 1:length(force_vals)
        force = force_vals(j);
        zcom = zcom_vals(j);
        if zcom > zcom_threshold
            bar(i, force, 'FaceColor', 'g');
        else
            bar(i, force, 'FaceColor', 'r');
        end
    end
end

I can attach or explain any other code or data that may help if it is needed.

Thanks in advance.

[dpb]

Knowing the precise content of the cell arrays would help, indeed. Attaching small sample dataset always helps folks actually do something specifically addressing the problem. As is, there's somewhat of a dilemma figuring out what you want -- whether the code is working as intended other than colors or what. Specifically, there are going to be length(weights)*length(force_vals) separate bars drawn with the nest loops but each is plotted only at the position of the outer loop? How many bars are there supposed to be, total?

If I understand the desire correctly, there would apparently would be only #weights bars, but each would consist of two segments, the section below the threshold and any above in red? It would seem that zcom_threshold is a constant, in which case that level will be the same for all? If this is the case and it is N bars with two segments each, the use the 'stacked' option where the input array to bar() will be a 2-row array of #weights columns; the bottom row the threshold value (constant) and the top the difference between the force and the threshold. But, this is an (how educated, I'm not sure) guess only...

Answer 1

[Mathieu NOE]

hello

maybe this ? (simple demo)

% stacked plot with threshold (lower => green, above th => red)
weigths = (1:10);
force = 2+weigths;
force_threshold = 6; 
y = zeros(2,numel(force));

a = min(force,force_threshold);  % force below or equal to force_threshold
b = force - a;                  % remaining portion above force_threshold
y = [a;b];                      % stack both arrays

h = bar(y', 'stacked');
set(h,{'FaceColor'},{'g';'r'});
xlabel('Weights')
ylabel('Force')

[dpb]

Yeah, @Mathieu NOE, that's the exact solution I was suggesting, but reading his earlier posting and the data he supplied there, I couldn't for the life of me figure out what the values he posted represented -- he had one case with something like 25 responses but only (he said) something like 6-7 weights. No idea how he was trying to visualize this; not having any idea what any of it means doesn't help, of course; lack of any context doesn't much help one to propose alternate approaches when the one taken doesn't seem to be going anywhere useful.

But, the above is certainly the easy/correct way to produce the stacked two-color bar; not the question is just how many of those are there supposed to be? And what are all the repetitions about?

[Mathieu NOE]

hello @dpb

thanks for the nice comments

I admit I didn't pay too much attention to some details in the original post as , as you, I coudn't figure out how the whole thing was supposed to work

so I opted for what I thought was a simple but close enough valuable answer

all the best

[Archie Baxter]

Sorry for the slow response, i have been away. This is something along the lines of what I was looking for thanks. However, there were four roboitc gripper types that i tested in the simulation, for each of these grippers the weight that was picked up during the simulation ranged from 1,2,5,10,20,30,50,100,200 kg. For each of these weights, a range of forces was applied to work out the minimum force required to lift the weight, therefore The data recorded is the force applied and the max z-CoM position of reach trial. The metric of success for the trial was a minimum z-CoM value and therefore i wanted to portray this in the bar graph whereby and force applied that did not exceed the z-CoM threshold was red, and if it was a successful trial, this was green. @dpb @Mathieu NOE