how to create an array of plots in App designer

I am using Matlab2019b and i am trying to create a real time plots, the number of plots displayed, depends on the user input parameters, so i defined a property

H_PLOT

;

then i created a for loop when a pushbutton is pressed

for i=1:1:app.num_of_channels
   figure;
   app.H_PLOT(1:app.num_of_channels) = plot(nan,nan, 'b'); 
end

but it gives me the following error:

"Assignment between unlike types is not allowed."

i dont understand why however it works well in normal m-code script but it doesnt work in app designer

[Cris LaPierre]

I have recreated an app in R2019b that does what you say you did but I do not get an error. Do you change the value of app.H_PLOT anywhere else?

Here's my (very simple) code.

    properties (Access = private)
        H_PLOT; % Description
    end
    

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

        % Button pushed function: Button
        function ButtonPushed(app, event)
            for i=1:1:2
               figure;
               app.H_PLOT(1:2) = plot(nan,nan, 'b'); 
            end
        end
    end

[Walter Roberson]

@ahmed abdel razik comments

Hello, i used your example and it works, but when i try to update the plot using timer as follow

 methods (Access = private)
     function timerFunction(app, ~, ~)
         if(app.Trig)
             app.Lamp.Color = app.BLACK_COLOR;
             app.Trig = 0;
         else
             app.Lamp.Color = app.GREEN_COLOR;
             app.Trig = 1;
         end
         for i=1:1:app.N
             app.H_PlOT(1:i).XData(app.index) = app.index;
             app.H_PlOT(1:i).YData(app.index) = app.index;
         end
         drawnow;
         app.index = app.index + 1;
     end
 end

i get the following error "Unrecognized method, property, or field 'H_PlOT' for class 'PLOT_ARRAY'."

[Walter Roberson]

It is not clear that you did

    properties (Access = private)
        H_PLOT; % Description
    end
    

[ahmed abdel razik]

Here is the full code:

classdef PLOT_ARRAY < matlab.apps.AppBase

    % Properties that correspond to app components
    properties (Access = public)
        UIFigure         matlab.ui.Figure
        Button           matlab.ui.control.Button
        NEditFieldLabel  matlab.ui.control.Label
        NEditField       matlab.ui.control.NumericEditField
        LampLabel        matlab.ui.control.Label
        Lamp             matlab.ui.control.Lamp
    end

    
    properties (Access = private)
        
        TIME_STEP = 1 % fixed time step of calling SendData function
        t % timer (for update GUI and send data)
        timer = 0;
        GREEN_COLOR = [0 1 0]
        RED_COLOR   = [1 0 0]
        BLACK_COLOR = [0 0 0]
        Trig = 0;
        index = 1;
        ref = 1;
        N = 0;
        h;
    end
    
    properties (Access = public)
        H_PLOT; % DescriptionH_PLOT; % Description
    end
    
    methods (Access = private)
        
        function timerFunction(app, ~, ~)
           if(app.Trig)
               app.Lamp.Color = app.BLACK_COLOR;
               app.Trig = 0;
           else
               app.Lamp.Color = app.GREEN_COLOR;
               app.Trig = 1;
           end
           for i=1:1:app.N
               app.H_PlOT.XData(1:app.index) = 1:app.index;
               app.H_PlOT.YData(1:app.index) = 1:app.index;
           end
           drawnow;
           app.index = app.index + 1;
        end
    end
    

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

        % Code that executes after component creation
        function startupFcn(app)
            app.t = timer;
            app.t.TimerFcn = @app.timerFunction;
            app.t.ExecutionMode = 'fixedRate';
            app.t.Period = app.TIME_STEP;
            app.t.BusyMode = 'drop';
        end

        % Button pushed function: Button
        function ButtonPushed(app, event)
            app.N = app.NEditField.Value;
            for i=1:1:app.N
               figure;
               app.H_PLOT = plot(nan,nan, 'b'); 
            end  
            start(app.t);
        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 = 'UI Figure';

            % Create Button
            app.Button = uibutton(app.UIFigure, 'push');
            app.Button.ButtonPushedFcn = createCallbackFcn(app, @ButtonPushed, true);
            app.Button.Position = [237 272 100 22];

            % Create NEditFieldLabel
            app.NEditFieldLabel = uilabel(app.UIFigure);
            app.NEditFieldLabel.HorizontalAlignment = 'right';
            app.NEditFieldLabel.Position = [197 325 25 22];
            app.NEditFieldLabel.Text = 'N';

            % Create NEditField
            app.NEditField = uieditfield(app.UIFigure, 'numeric');
            app.NEditField.Position = [237 325 100 22];

            % Create LampLabel
            app.LampLabel = uilabel(app.UIFigure);
            app.LampLabel.HorizontalAlignment = 'right';
            app.LampLabel.Position = [267 230 35 22];
            app.LampLabel.Text = 'Lamp';

            % Create Lamp
            app.Lamp = uilamp(app.UIFigure);
            app.Lamp.Position = [317 230 20 20];

            % 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 = PLOT_ARRAY

            % Create UIFigure and components
            createComponents(app)

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

            % Execute the startup function
            runStartupFcn(app, @startupFcn)

            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

Answer 1

[Walter Roberson]

In the lines

               app.H_PlOT.XData(1:app.index) = 1:app.index;
               app.H_PlOT.YData(1:app.index) = 1:app.index;

You are referring to H_PlOT instead of to H_PLOT . That is, you are using lower-case L instead of upper-case L.

[ahmed abdel razik]

I did that, and i got the following error when i run it

"Unable to perform assignment because dot indexing is not supported for variables of this type."

[Walter Roberson]

What sequence of events or commands are you using to get that? I tried it and just got a blinking light.

[ahmed abdel razik]

I just run this code, set the number to 3 and press the button

classdef PLOT_ARRAY < matlab.apps.AppBase

    % Properties that correspond to app components
    properties (Access = public)
        UIFigure         matlab.ui.Figure
        Button           matlab.ui.control.Button
        NEditFieldLabel  matlab.ui.control.Label
        NEditField       matlab.ui.control.NumericEditField
        LampLabel        matlab.ui.control.Label
        Lamp             matlab.ui.control.Lamp
    end

    
    properties (Access = private)
        
        TIME_STEP = 1 % fixed time step of calling SendData function
        t % timer (for update GUI and send data)
        timer = 0;
        GREEN_COLOR = [0 1 0]
        RED_COLOR   = [1 0 0]
        BLACK_COLOR = [0 0 0]
        Trig = 0;
        index = 1;
        ref = 1;
        N = 0;
        h;
    end
    
    properties (Access = public)
        H_PLOT; % DescriptionH_PLOT; % Description
    end
    
    methods (Access = private)
        
        function timerFunction(app, ~, ~)
           if(app.Trig)
               app.Lamp.Color = app.BLACK_COLOR;
               app.Trig = 0;
           else
               app.Lamp.Color = app.GREEN_COLOR;
               app.Trig = 1;
           end
           for i=1:1:app.N
               app.H_PLOT(i).XData(1:app.index) = 1:app.index;
               app.H_PLOT(i).YData(1:app.index) = 1:app.index;
           end
           drawnow;
           app.index = app.index + 1;
        end
    end
    

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

        % Code that executes after component creation
        function startupFcn(app)
            app.t = timer;
            app.t.TimerFcn = @app.timerFunction;
            app.t.ExecutionMode = 'fixedRate';
            app.t.Period = app.TIME_STEP;
            app.t.BusyMode = 'drop';
        end

        % Button pushed function: Button
        function ButtonPushed(app, event)
            app.N = app.NEditField.Value;
            for i=1:1:app.N
               figure;
               app.H_PLOT(i) = plot(nan,nan, 'b'); 
            end  
            start(app.t);
        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 = 'UI Figure';

            % Create Button
            app.Button = uibutton(app.UIFigure, 'push');
            app.Button.ButtonPushedFcn = createCallbackFcn(app, @ButtonPushed, true);
            app.Button.Position = [237 272 100 22];

            % Create NEditFieldLabel
            app.NEditFieldLabel = uilabel(app.UIFigure);
            app.NEditFieldLabel.HorizontalAlignment = 'right';
            app.NEditFieldLabel.Position = [197 325 25 22];
            app.NEditFieldLabel.Text = 'N';

            % Create NEditField
            app.NEditField = uieditfield(app.UIFigure, 'numeric');
            app.NEditField.Position = [237 325 100 22];

            % Create LampLabel
            app.LampLabel = uilabel(app.UIFigure);
            app.LampLabel.HorizontalAlignment = 'right';
            app.LampLabel.Position = [267 230 35 22];
            app.LampLabel.Text = 'Lamp';

            % Create Lamp
            app.Lamp = uilamp(app.UIFigure);
            app.Lamp.Position = [317 230 20 20];

            % 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 = PLOT_ARRAY

            % Create UIFigure and components
            createComponents(app)

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

            % Execute the startup function
            runStartupFcn(app, @startupFcn)

            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