Only last iteration of for loop

Hello,

I am running a for loop in a while loop in app designer which may not be good programming practice but I really need it to run. I am ploting a bar chart in the for loop because i need various colors for different bars. * while loop because am constantly reading serial data from a com port using the serial port fronctions.

Only the last bar is plotted when i run the code. Displaying b on the gui is always 3. I fixed b to 2 and the second bar showed up. I would be very happy to get your ideas on y this is happening. Not just for the code to run but also for future reference. Thanks

Below is my code

   properties (Access = public)
        % Battery represenstation
        
         Batteries = reordercats(categorical({'Battery1','Battery2','Battery3'}));  % x values
         y = [Volt1, Volt2, Volt3]; % y Values
         clr = [0.2 0.71 0.3; 0.25 0.55 0.79; 0.9  0.1 0.14]; % colors
         
         end
 myBar = zeros((lenth(Batteries)));
                
while(1)
    for b = 1:length(y)
         app.BEditField.Value = b; % display b on GUI
         % Plot one single bar as a separate bar series.
         myBar(b) = bar(app.UIAxes, app.Batteries(b), y(b));
                    
         % Apply the color to this bar series.
          set(myBar(b),'FaceColor', app.clr(b,:));
         % values on each bar           
         text(app.UIAxes, b:b, y(b)', num2str(y(b)','%0.2f'),'HorizontalAlignment','center','VerticalAlignment','bottom')
         hold on ;
    end
end

Answer 1

[Cris LaPierre]

I think the reson you are only getting the final bar is because your hold on is not being applied to your UIAxes. In app designer, you always have to specify the target axes. Try this

hold(app.UIAxes,'on')

Note that it is best practice to pair every hold on with a corresponding hold off. Here, that should probably go outside the for loop, but inside the while loop. Otherwise, your bars will continue to be plotted on top of the previous loop's.

However, you don't need to use hold at all. My recommendation would be to add a startupfcn that creates the bar graph when the app starts.

app.myBar = bar(app.UIAxes, app.Batteries, zeros(1,3));
app.myBar.CData(1,:) = clr(1,:);
app.myBar.CData(2,:) = clr(2,:);
app.myBar.CData(3,:) = clr(3,:);

Then have your loop just update the YData property of each bar.

app.myBar(b).YData = y(b);
drawnow

[Kizito Amungwa Achembong]

Thanks very much. That was excatly the issue. The code runs fine and am also grateful for the recommendation.

[Kizito Amungwa Achembong]

Also, I wish to ask if there is a more efficient way to represent a battery state of charge graphically on a GUI. I will like to have something that looks like a battery and changes level as it charges and discharges (Just like on an Iphone) and in a modular way so that i can show x number of batteries without changing a lot on the code. I am presently using the bar graph which works (thanks to you) but i guess there is a more efficient way.

[Cris LaPierre]

Depends what you mean by efficient. The most effecient way to me is to use something MATLAB already provides a function for (e.g. bar plot). Getting closer to what you are describing would require developing a solution yourself. That's certainly possible, and wouldn't necessarily be computationally expensive, but not sure it would qualify as efficient.

It just matters on how you value that over the current approach.