MATLAB GUI not showing errors but not displaying results when pushbutton is clicked

% --- Executes on button press in estimate.
function estimate_Callback(hObject, eventdata, handles)
% hObject    handle to estimate (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)

valyearmenu = get(hObject,'Value');
stryearmenu = get(hObject,'String');
valvehiclemenu = get(hObject,'Value');
strvehiclemenu = get(hObject,'String');

switch stryearmenu(valyearmenu)
    case '2018'
        switch strvehiclemenu(valvehiclemenu)
            case 'Private'
                L = str2num(get(handles.length,'String'));
                V = str2num(get(handles.velocity,'String'));
                Q = str2num(get(handles.flowrate,'String'));
                c = 524;
                C = num2str(Q*(L/V)*(c/60)*365);
                set(handles.cost,'String',C);
            case 'Jeepneys'
                L = str2num(get(handles.length,'String'));
                V = str2num(get(handles.velocity,'String'));
                Q = str2num(get(handles.flowrate,'String'));
                c = 737;
                C = num2str(Q*(L/V)*(c/60)*365);
                set(handles.cost,'String',C);
            case 'Buses'
                L = str2num(get(handles.length,'String'));
                V = str2num(get(handles.velocity,'String'));
                Q = str2num(get(handles.flowrate,'String'));
                c = 2410;
                C = num2str(Q*(L/V)*(c/60)*365);
                set(handles.cost,'String',C);
            case 'Trucks'
                L = str2num(get(handles.length,'String'));
                V = str2num(get(handles.velocity,'String'));
                Q = str2num(get(handles.flowrate,'String'));
                c = 1381;
                C = num2str(Q*(L/V)*(c/60)*365);
                set(handles.cost,'String',C);
        end
    case '2019'
        switch vehiclemenu
            case 'Private'
                L = str2num(get(handles.length,'String'));
                V = str2num(get(handles.velocity,'String'));
                Q = str2num(get(handles.flowrate,'String'));
                c = 545;
                C = num2str(Q*(L/V)*(c/60)*365);
                set(handles.cost,'String',C);
            case 'Jeepneys'
                L = str2num(get(handles.length,'String'));
                V = str2num(get(handles.velocity,'String'));
                Q = str2num(get(handles.flowrate,'String'));
                c = 767;
                C = num2str(Q*(L/V)*(c/60)*365);
                set(handles.cost,'String',C);
            case 'Buses'
                L = str2num(get(handles.length,'String'));
                V = str2num(get(handles.velocity,'String'));
                Q = str2num(get(handles.flowrate,'String'));
                c = 2509;
                C = num2str(Q*(L/V)*(c/60)*365);
                set(handles.cost,'String',C);
            case 'Trucks'
                L = str2num(get(handles.length,'String'));
                V = str2num(get(handles.velocity,'String'));
                Q = str2num(get(handles.flowrate,'String'));
                c = 1473;
                C = num2str(Q*(L/V)*(c/60)*365);
                set(handles.cost,'String',C);
        end
    case '2020'
        switch vehiclemenu
            case 'Private'
                L = str2num(get(handles.length,'String'));
                V = str2num(get(handles.velocity,'String'));
                Q = str2num(get(handles.flowrate,'String'));
                c = 567;
                C = num2str(Q*(L/V)*(c/60)*365);
                set(handles.cost,'String',C);
            case 'Jeepneys'
                L = str2num(get(handles.length,'String'));
                V = str2num(get(handles.velocity,'String'));
                Q = str2num(get(handles.flowrate,'String'));
                c = 797;
                C = num2str(Q*(L/V)*(c/60)*365);
                set(handles.cost,'String',C);
            case 'Buses'
                L = str2num(get(handles.length,'String'));
                V = str2num(get(handles.velocity,'String'));
                Q = str2num(get(handles.flowrate,'String'));
                c = 2607;
                C = num2str(Q*(L/V)*(c/60)*365);
                set(handles.cost,'String',C);
            case 'Trucks'
                L = str2num(get(handles.length,'String'));
                V = str2num(get(handles.velocity,'String'));
                Q = str2num(get(handles.flowrate,'String'));
                c = 1494;
                C = num2str(Q*(L/V)*(c/60)*365);
                set(handles.cost,'String',C);
        end
    case '2021'
        switch vehiclemenu
            case 'Private'
                L = str2num(get(handles.length,'String'));
                V = str2num(get(handles.velocity,'String'));
                Q = str2num(get(handles.flowrate,'String'));
                c = 603;
                C = num2str(Q*(L/V)*(c/60)*365);
                set(handles.cost,'String',C);
            case 'Jeepneys'
                L = str2num(get(handles.length,'String'));
                V = str2num(get(handles.velocity,'String'));
                Q = str2num(get(handles.flowrate,'String'));
                c = 847;
                C = num2str(Q*(L/V)*(c/60)*365);
                set(handles.cost,'String',C);
            case 'Buses'
                L = str2num(get(handles.length,'String'));
                V = str2num(get(handles.velocity,'String'));
                Q = str2num(get(handles.flowrate,'String'));
                c = 2771;
                C = num2str(Q*(L/V)*(c/60)*365);
                set(handles.cost,'String',C);
            case 'Trucks'
                L = str2num(get(handles.length,'String'));
                V = str2num(get(handles.velocity,'String'));
                Q = str2num(get(handles.flowrate,'String'));
                c = 1587;
                C = num2str(Q*(L/V)*(c/60)*365);
                set(handles.cost,'String',C);
        end
    case '2022'
        switch vehiclemenu
            case 'Private'
                L = str2num(get(handles.length,'String'));
                V = str2num(get(handles.velocity,'String'));
                Q = str2num(get(handles.flowrate,'String'));
                c = 638;
                C = num2str(Q*(L/V)*(c/60)*365);
                set(handles.cost,'String',C);
            case 'Jeepneys'
                L = str2num(get(handles.length,'String'));
                V = str2num(get(handles.velocity,'String'));
                Q = str2num(get(handles.flowrate,'String'));
                c = 897;
                C = num2str(Q*(L/V)*(c/60)*365);
                set(handles.cost,'String',C);
            case 'Buses'
                L = str2num(get(handles.length,'String'));
                V = str2num(get(handles.velocity,'String'));
                Q = str2num(get(handles.flowrate,'String'));
                c = 2935;
                C = num2str(Q*(L/V)*(c/60)*365);
                set(handles.cost,'String',C);
            case 'Trucks'
                L = str2num(get(handles.length,'String'));
                V = str2num(get(handles.velocity,'String'));
                Q = str2num(get(handles.flowrate,'String'));
                c = 1681;
                C = num2str(Q*(L/V)*(c/60)*365);
                set(handles.cost,'String',C);
        end
    case '2023'
        switch vehiclemenu
            case 'Private'
                L = str2num(get(handles.length,'String'));
                V = str2num(get(handles.velocity,'String'));
                Q = str2num(get(handles.flowrate,'String'));
                c = 674;
                C = num2str(Q*(L/V)*(c/60)*365);
                set(handles.cost,'String',C);
            case 'Jeepneys'
                L = str2num(get(handles.length,'String'));
                V = str2num(get(handles.velocity,'String'));
                Q = str2num(get(handles.flowrate,'String'));
                c = 947;
                C = num2str(Q*(L/V)*(c/60)*365);
                set(handles.cost,'String',C);
            case 'Buses'
                L = str2num(get(handles.length,'String'));
                V = str2num(get(handles.velocity,'String'));
                Q = str2num(get(handles.flowrate,'String'));
                c = 3099;
                C = num2str(Q*(L/V)*(c/60)*365);
                set(handles.cost,'String',C);
            case 'Trucks'
                L = str2num(get(handles.length,'String'));
                V = str2num(get(handles.velocity,'String'));
                Q = str2num(get(handles.flowrate,'String'));
                c = 1775;
                C = num2str(Q*(L/V)*(c/60)*365);
                set(handles.cost,'String',C);
        end
    case '2024'
        switch vehiclemenu
            case 'Private'
                L = str2num(get(handles.length,'String'));
                V = str2num(get(handles.velocity,'String'));
                Q = str2num(get(handles.flowrate,'String'));
                c = 709;
                C = num2str(Q*(L/V)*(c/60)*365);
                set(handles.cost,'String',C);
            case 'Jeepneys'
                L = str2num(get(handles.length,'String'));
                V = str2num(get(handles.velocity,'String'));
                Q = str2num(get(handles.flowrate,'String'));
                c = 997;
                C = num2str(Q*(L/V)*(c/60)*365);
                set(handles.cost,'String',C);
            case 'Buses'
                L = str2num(get(handles.length,'String'));
                V = str2num(get(handles.velocity,'String'));
                Q = str2num(get(handles.flowrate,'String'));
                c = 3263;
                C = num2str(Q*(L/V)*(c/60)*365);
                set(handles.cost,'String',C);
            case 'Trucks'
                L = str2num(get(handles.length,'String'));
                V = str2num(get(handles.velocity,'String'));
                Q = str2num(get(handles.flowrate,'String'));
                c = 1869;
                C = num2str(Q*(L/V)*(c/60)*365);
                set(handles.cost,'String',C);
        end
    case '2025'
        switch vehiclemenu
            case 'Private'
                L = str2num(get(handles.length,'String'));
                V = str2num(get(handles.velocity,'String'));
                Q = str2num(get(handles.flowrate,'String'));
                c = 745;
                C = num2str(Q*(L/V)*(c/60)*365);
                set(handles.cost,'String',C);
            case 'Jeepneys'
                L = str2num(get(handles.length,'String'));
                V = str2num(get(handles.velocity,'String'));
                Q = str2num(get(handles.flowrate,'String'));
                c = 1048;
                C = num2str(Q*(L/V)*(c/60)*365);
                set(handles.cost,'String',C);
            case 'Buses'
                L = str2num(get(handles.length,'String'));
                V = str2num(get(handles.velocity,'String'));
                Q = str2num(get(handles.flowrate,'String'));
                c = 3427;
                C = num2str(Q*(L/V)*(c/60)*365);
                set(handles.cost,'String',C);
            case 'Trucks'
                L = str2num(get(handles.length,'String'));
                V = str2num(get(handles.velocity,'String'));
                Q = str2num(get(handles.flowrate,'String'));
                c = 1963;
                C = num2str(Q*(L/V)*(c/60)*365);
                set(handles.cost,'String',C);
        end
end

guidata(hObject,handles);

[Dennis]

I might be confusing something, but this looks really odd to me:

valyearmenu = get(hObject,'Value');
stryearmenu = get(hObject,'String');
valvehiclemenu = get(hObject,'Value');
strvehiclemenu = get(hObject,'String');
switch stryearmenu(valyearmenu)
   
end

From the picture i would guess your pushbutton fires this callback. So valyearmenu would be 'Estimate' and the value could be set at any point (seems odd for a button to have one though). I would assume stryearmenu(valyearmenu) to be empty (0 index) or a combination of chars from the word 'Estimate' (if a value was set somewhere). It will never be '2018' or any of the other cases.

Edit:

Since you are getting the value and string of the same object valyearmenu and valvehiclemenu are equal. It is impossible for them to have different values in your switch statements.

You most likely want to get the selected value of your listboxes, which could be done with

valyearmenu=get(handles.MyListboxHandle,'value');
valvehiclemenu = get(handles.myOtherListboxHandle,'value');

Please keep in mind that i have no idea what the names of your listbox handles are.

[Adam Danz]

I also suggested that this switch case didn't match the pattern of the other switch cases so Lexa, you should look into that and decide if that's what your code is supposed to be doing.

Answer 1

[Adam Danz]

My guess is that one of your variables (Q, L V, ...) is empty. When you pass an empty through str2num() it produces an empty vector. If you use an empty vector in a computation, the result will be empty. When you convert an empty vector to a string, the string will also be empty. So you're probably writing an empty string to handles.cost.

x = str2num(' ');   % x = []
C = x * 2;          % y = []; 
str =  num2str(C);  %str = 0×0 empty char array

To troubleshoot, make sure you have numerical values in L, V, Q and make sure C is a non-empty string.

[Lexa]

But my variable Q, V and L are input values and when I input values on their corresponding edit textbox nothing happens. Does that not mean that they are not empty? Sorry, I recently just started using MATLAB please bare with my knowledge about this. Here is a screenshot of my fig.file:

[Adam Danz]

This is where matlab's debugging tools (<-link) come in handy and the time you will save after learning how to use them will be much greater than the time spent trying to find solutions without the debug tool. In the meantime, here's a simple way to test what I recommended.

1) at the end of your callback function, include this line then save.

fprintf('L= %.5f; V=%.5f; Q=%.5f; C=%s\n',L,V,Q,C); 

2) Close your GUI and reopen it

3) enter values into all edit boxes in your GUI and then run the callbackfunction by pressing the button. In the command window you should see a line printed with the values of L V Q and C. L V and Q will show up to 5 decimal places.

This will help you confirmat that your callback function is receiving the data you intend it to recieve and is doing the conversions you expect.

[Lexa]

Thank you for the response. I tried your suggestion and here is the error I got:

Does this mean that there is something that I'm doing wrong with my variable 'L'? If so, what can I do to fix it?

[Adam Danz]

Ah, ok, we're getting closer. If the fprintf command is at the end of the callback function and you're getting that error, that means L is never defined within the function. That means none of your cases are being met. This is why you should always include an 'otherwise' case at the end of each switch (see help switch).

So, you need to figure out which case should have been met and why it's not being met.

[Lexa]

Hi again, I tried the otherwise case but still getting the same about regarding variable 'L' though my static textbox (cost) is now showing the value I assigned for the other wise case. I don't understand why the variable 'L' is undefined within this function.

switch strvehiclemenu(valvehiclemenu)
            case Private
                L = str2num(get(handles.length,'String'));
                V = str2num(get(handles.velocity,'String'));
                Q = str2num(get(handles.flowrate,'String'));
                c = 524;
                C = (Q*(L/V)*(c/60)*365);
                set(handles.cost,'String',num2str(C));
            case Jeepneys
                L = str2num(get(handles.length,'String'));
                V = str2num(get(handles.velocity,'String'));
                Q = str2num(get(handles.flowrate,'String'));
                c = 737;
                C = (Q*(L/V)*(c/60)*365);
                set(handles.cost,'String',(C));
            case Buses
                L = str2num(get(handles.length,'String'));
                V = str2num(get(handles.velocity,'String'));
                Q = str2num(get(handles.flowrate,'String'));
                c = 2410;
                C = (Q*(L/V)*(c/60)*365);
                set(handles.cost,'String',num2str(C));
            case Trucks
                L = str2num(get(handles.length,'String'));
                V = str2num(get(handles.velocity,'String'));
                Q = str2num(get(handles.flowrate,'String'));
                c = 1381;
                C = (Q*(L/V)*(c/60)*365);
                set(handles.cost,'String',num2str(C));
            otherwise
                set(handles.cost,'String',num2str(0));
    end

[Lexa]

Also, as an update, I defined my variables L, V, and Q outside the switch statementd it seems to be working for now, but now my problem is defining my constant 'c' outside the switch statement. All I know about defining a constant is equating the variable to its equivalent numerical value but I don't know how to define it if its varying depending on the menu in my gui. I hope you can also help me with this one.

[Adam Danz]

It seems you don't understand how switch/case works.

https://www.mathworks.com/help/matlab/ref/switch.html

You need to understand that before you can fix your code. The 'otherwise' case is usually used to load default values for when none of the cases are met or it's commonly used to throw an error when none of the cases are met.

In your case, the problem is that none of your cases are met and you need to figure out why.

In other words, whatever value is "stryearmenu(valyearmenu)", you don't have a case that matches the value --OR-- there is no case that matches the value of vehiclemenu.

One thing I noticed that you should look into. All of your 2nd-level cases are "vehiclemenu" except for the first which is "strvehiclemenu(valvehiclemenu)". Is that the problem?

[Adam Danz]

"I'm a beginner to Matlab and have no idea what I'm doing. Right now I'm just doing trial and error and see if anything works. The "strvehiclemenu(valvehiclemenu)" seem to have no effect when written for every 2nd-level switch statement."

Troubleshooting by using trial and error is a bad idea. Just because a code "works" and doesn't throw an error doesn't mean that the code is doing what it's designed for.

Instead, you should take time to read the documentation an undestand the inputs and outputs of a function and how to use a function. You're lucky because the only function you need to understand is the switch/case.

To help you troubleshoot, please run the original code you posted in your question but I'd like you to remove the semicolons (;) after the first 4 lines (below) so that their values print to the command window. Then copy the values for each of those 4 variables and paste them here as a comment.

valyearmenu = get(hObject,'Value')
stryearmenu = get(hObject,'String')
valvehiclemenu = get(hObject,'Value')
strvehiclemenu = get(hObject,'String')

[madhan ravi]

Lexa's answer moved here for consistency:

I'm a beginner to Matlab and have no idea what I'm doing. Right now I'm just doing trial and error and see if anything works. The "strvehiclemenu(valvehiclemenu)" seem to have no effect when written for every 2nd-level switch statement.