Index exceeds the number of array elements (0)

Hello. I'm having this error in my code and I can't get why. I am trying to make it so if the user doesn't move the analog stick, the drone is hovering in its' place

        function [] = calcThrust(app)
            if (app.remoteState.Gamepad.LeftThumbY > 5000 || app.remoteState.Gamepad.LeftThumbY < -5000)
              

                app.droneThrust = (app.maxDroneThrust - app.hoverThrust) * double(app.remoteState.Gamepad.LeftThumbY) / 32768 + app.hoverThrust;
                   
                if app.droneThrust < -app.maxDroneThrust % Descending
                    app.droneThrust = -app.maxDroneThrust;
                elseif app.droneThrust > app.maxDroneThrust
                    app.droneThrust = app.maxDroneThrust;
                end
                
                if (app.droneThrust < app.hoverThrust) & (app.dronePos(3) <= app.minHoverHeight)
                    app.droneThrust = app.hoverThrust; 
                    % disp(app.droneThrust + " " + app.dronePos(3));
                end
            else
                app.droneThrust = app.hoverThrust; % <- The error is in this line
            end
        end
        

The error is in line "app.droneThrust = app.hoverThrust;", if I comment this line everything works. I don't understand why, because both of these variables are numbers and not indexed..

[Mario Malic]

Where did you define the value for your property hoverThrust?

[Avi Michaely]

    properties (Access = public)
        ....
    hoverThrust; 
    end
    
    
    function startupFcn(app) % Called when app starts
        app.hoverThrust = app.droneWeightKG * app.earthGravity; % 1mg
    end

[Mario Malic]

Both of these app.droneWeightKG, app.earthGravity are also correctly defined?

If one of the variables is empty, then resulting variable will be empty as well, which will throw the error in your title. If you defined them correctly, then you should check debugging. Set a breakpoint at that line and check the values in the workspace.

[Avi Michaely]

Yep, they are both constants:

droneWeightKG = 0.905; % drone weight.. in kg

earthGravity = 9.819; % [m /s^2]

I'll try debugging and see what happens

EDIT: Thanks! When debugging I saw hoverThrust is 0x0 double because I called the timers before defining hoverThrust in the startup function, I switched the order and now it works! :)

Answer 1

[Mario Malic]

If earthGravity and hoverThrust are not properties of the app, then that's why it doesn't work.

properties (Access = public)
    droneWeightKG
    earthGravity
    hoverThrust
end
    
function startupFcn(app)   
    app.droneWeightKG = 0.905;              % drone weight.. in kg
    app.earthGravity = 9.819;               % [m /s^2]
end

You can define them as varuables in the calcThrust function, but then you'd have to change some of the code, above might be more appropriate solution, depending on the complexity of the app.