Error with my CODE and I don't know why.

 % Properties that correspond to app components
    properties (Access = public)
        UIFigure              matlab.ui.Figure
        R1EditFieldLabel      matlab.ui.control.Label
        R1EditField           matlab.ui.control.EditField
        R2EditFieldLabel      matlab.ui.control.Label
        R2EditField           matlab.ui.control.EditField
        R3EditFieldLabel      matlab.ui.control.Label
        R3EditField           matlab.ui.control.EditField
        ResistorsLabel        matlab.ui.control.Label
        V1EditFieldLabel      matlab.ui.control.Label
        V1EditField           matlab.ui.control.EditField
        V2EditFieldLabel      matlab.ui.control.Label
        V2EditField           matlab.ui.control.EditField
        CalculateButton       matlab.ui.control.Button
        I1EditFieldLabel      matlab.ui.control.Label
        I1EditField           matlab.ui.control.EditField
        I2EditFieldLabel      matlab.ui.control.Label
        I2EditField           matlab.ui.control.EditField
        I3EditFieldLabel      matlab.ui.control.Label
        I3EditField           matlab.ui.control.EditField
        VoltagesourcesLabel   matlab.ui.control.Label
        OutputcurrentsALabel  matlab.ui.control.Label
    end

    % Callbacks that handle component events
    methods (Access = private)

        % Button pushed function: CalculateButton
        function CalculateButtonPushed(app, event)
           R1 = app.R1EditField.Value;
           R2 = app.R2EditField.Value;
           R3 = app.R3EditField.Value;
           
           V1 = app.V1EditField.Value;
           V2 = app.V2EditField.Value;
           
           syms I1 I2 I3;
           eqn1 = I1*R1 + I2*R2 == V2 - V1;
           eqn2 = I2*R2 + I3*R3 == V2;
           eqn3 = I1 + I3 - I2 == 0;
           
           [A,B] = equationsToMatrix([eqn1, eqn2, eqn3], [I1, I2, I3]);
           X = linsolve(A,B);
           
           app.I1EditField.Value = double(X(1));
           app.I2EditField.Value = double(X(2));
           app.I3EditField.Value = double(X(3));
        end
    end

    % Component initialization
    methods (Access = private)

        % Create UIFigure and components
        function createComponents(app)

            % Create UIFigure and hide until all components are created
            app.UIFigure = uifigure('Visible', 'off');
            app.UIFigure.Position = [100 100 640 480];
            app.UIFigure.Name = 'MATLAB App';

            % Create R1EditFieldLabel
            app.R1EditFieldLabel = uilabel(app.UIFigure);
            app.R1EditFieldLabel.HorizontalAlignment = 'right';
            app.R1EditFieldLabel.Position = [46 329 25 22];
            app.R1EditFieldLabel.Text = 'R1';

            % Create R1EditField
            app.R1EditField = uieditfield(app.UIFigure, 'text');
            app.R1EditField.Position = [86 329 100 22];

            % Create R2EditFieldLabel
            app.R2EditFieldLabel = uilabel(app.UIFigure);
            app.R2EditFieldLabel.HorizontalAlignment = 'right';
            app.R2EditFieldLabel.Position = [53 270 25 22];
            app.R2EditFieldLabel.Text = 'R2';

            % Create R2EditField
            app.R2EditField = uieditfield(app.UIFigure, 'text');
            app.R2EditField.Position = [93 270 100 22];

            % Create R3EditFieldLabel
            app.R3EditFieldLabel = uilabel(app.UIFigure);
            app.R3EditFieldLabel.HorizontalAlignment = 'right';
            app.R3EditFieldLabel.Position = [54 208 25 22];
            app.R3EditFieldLabel.Text = 'R3';

            % Create R3EditField
            app.R3EditField = uieditfield(app.UIFigure, 'text');
            app.R3EditField.Position = [94 208 100 22];

            % Create ResistorsLabel
            app.ResistorsLabel = uilabel(app.UIFigure);
            app.ResistorsLabel.Position = [105 375 56 22];
            app.ResistorsLabel.Text = 'Resistors';

            % Create V1EditFieldLabel
            app.V1EditFieldLabel = uilabel(app.UIFigure);
            app.V1EditFieldLabel.HorizontalAlignment = 'right';
            app.V1EditFieldLabel.Position = [326 316 25 22];
            app.V1EditFieldLabel.Text = 'V1';

            % Create V1EditField
            app.V1EditField = uieditfield(app.UIFigure, 'text');
            app.V1EditField.Position = [366 316 100 22];

            % Create V2EditFieldLabel
            app.V2EditFieldLabel = uilabel(app.UIFigure);
            app.V2EditFieldLabel.HorizontalAlignment = 'right';
            app.V2EditFieldLabel.Position = [331 270 25 22];
            app.V2EditFieldLabel.Text = 'V2';

            % Create V2EditField
            app.V2EditField = uieditfield(app.UIFigure, 'text');
            app.V2EditField.Position = [371 270 100 22];

            % Create CalculateButton
            app.CalculateButton = uibutton(app.UIFigure, 'push');
            app.CalculateButton.ButtonPushedFcn = createCallbackFcn(app, @CalculateButtonPushed, true);
            app.CalculateButton.Position = [227 144 100 22];
            app.CalculateButton.Text = 'Calculate';

            % Create I1EditFieldLabel
            app.I1EditFieldLabel = uilabel(app.UIFigure);
            app.I1EditFieldLabel.HorizontalAlignment = 'right';
            app.I1EditFieldLabel.Position = [31 67 25 22];
            app.I1EditFieldLabel.Text = 'I1';

            % Create I1EditField
            app.I1EditField = uieditfield(app.UIFigure, 'text');
            app.I1EditField.Position = [70 67 100 22];

            % Create I2EditFieldLabel
            app.I2EditFieldLabel = uilabel(app.UIFigure);
            app.I2EditFieldLabel.HorizontalAlignment = 'right';
            app.I2EditFieldLabel.Position = [213 67 25 22];
            app.I2EditFieldLabel.Text = 'I2';

            % Create I2EditField
            app.I2EditField = uieditfield(app.UIFigure, 'text');
            app.I2EditField.Position = [253 67 100 22];

            % Create I3EditFieldLabel
            app.I3EditFieldLabel = uilabel(app.UIFigure);
            app.I3EditFieldLabel.HorizontalAlignment = 'right';
            app.I3EditFieldLabel.Position = [425 67 25 22];
            app.I3EditFieldLabel.Text = 'I3';

            % Create I3EditField
            app.I3EditField = uieditfield(app.UIFigure, 'text');
            app.I3EditField.Position = [465 67 100 22];

            % Create VoltagesourcesLabel
            app.VoltagesourcesLabel = uilabel(app.UIFigure);
            app.VoltagesourcesLabel.Position = [396 354 91 22];
            app.VoltagesourcesLabel.Text = 'Voltage sources';

            % Create OutputcurrentsALabel
            app.OutputcurrentsALabel = uilabel(app.UIFigure);
            app.OutputcurrentsALabel.Position = [224 105 108 22];
            app.OutputcurrentsALabel.Text = 'Output currents (A)';

            % Show the figure after all components are created
            app.UIFigure.Visible = 'on';
        end
    end

    % App creation and deletion
    methods (Access = public)

        % Construct app
        function app = Exercise4_Marcelo

            % Create UIFigure and components
            createComponents(app)

            % Register the app with App Designer
            registerApp(app, app.UIFigure)

            if nargout == 0
                clear app
            end
        end

        % Code that executes before app deletion
        function delete(app)

            % Delete UIFigure when app is deleted
            delete(app.UIFigure)
        end
    end
end

Note: this is what indicates "Error using matlab.ui.control.EditField/set.Value (line 98)

'Value' must be a character vector or a string scalar."

[Mohsin Zubair]

Try using num2str(Your value) also it would be better to share your entire app because sharing all this code like this we can't find the error ourselves.

Answer 1

[Shiva Kalyan Diwakaruni]

Hi,

the error message indicates that the Edit Field's Value must be a character vector or string. MATLAB does not automatically convert a variable to a char, but you can do so by using the "char" function. To do this, you need to change the line:

app.seriesEditField.Value = yy;

to:

app.seriesEditField.Value = char(yy);

If you intend for your variable to be displayed as a number, you may be better served by creating a Numeric Edit Field in your app and converting to double instead of char. You can find the Numeric Edit Field in the Component Library just above the Text Edit Field. Your line of code would then become:

app.seriesEditField.Value = double(yy);

Hope it helps.