How to take a "differential equation" as input from user in matlab appdesigner?

hi,

I am working on a app where user will insert a differential equation with initial conditions and the output will be the solution of the differential equation.I am confused which edit field to use to accept the differential equation from user.

let the equation,

y"+3y'+2y=sin(t)

y(0)=0,y'(0)=1

kindly share the code to solve this problem.thank you.

In matlab,this is the code how i solve the problem(the method is called EXPLICIT SOLUTION).But how to take this DE as input in appdesigner?/

eqn='D2y+3*Dy+2*y=sin(t)';
init='y(0)=0,Dy(0)=0';
y=dsolve(eqn,init)

last line returns the solution of this differential equation.

[Walter Roberson]

Please note that that form of dsolve() is going to be discontinued soon. You should be constructing symbolic expressions using diff() . In turn you might use str2sym() on a quoted string. For example

eqn = str2sym('diff(y(t),t,t) + 3 * diff(y(t),t) + 2*y(t) == sin(t)')

eqn = 

dsolve(eqn)

ans = 

Answer 1

[Alberto Cuadra Lara]

Hi Himalay,

As @Walter Roberson commented, support of character vectors and strings will be removed in a future release. Anyway, here's an app with that format implemented. You should adapt it to the new format for compatibility. I have included also the option to plot the solution of the ODE for a given range.

Best,

Alberto

classdef example_ODE_app < matlab.apps.AppBase
    % Author: Alberto Cuadra-Lara
    % PhD Candidate - Dpto. Ingeniería Térmica y de Fluidos
    % Office: 1.1.D23, Universidad Carlos III de Madrid
    
    % Properties that correspond to app components
    properties (Access = public)
        UIFigure                      matlab.ui.Figure
        GridLayout                    matlab.ui.container.GridLayout
        range                         matlab.ui.control.EditField
        RangeEditFieldLabel           matlab.ui.control.Label
        solution                      matlab.ui.control.TextArea
        SolutionTextAreaLabel         matlab.ui.control.Label
        initial_conditions            matlab.ui.control.EditField
        InitialconditionsEditFieldLabel  matlab.ui.control.Label
        ode                           matlab.ui.control.EditField
        OrdDifferentialequationLabel  matlab.ui.control.Label
        PlotButton                    matlab.ui.control.Button
        ClearButton                   matlab.ui.control.Button
        CalculateButton               matlab.ui.control.Button
    end

    
    properties (Access = private)
        ode_solution % ODE solution [symbolic]
    end
    

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

        % Button pushed function: CalculateButton
        function CalculateButtonPushed(app, event)
            % Get inputs
            eqn = app.ode.Value;
            init = app.initial_conditions.Value;
            % Solve ODE
            app.ode_solution = dsolve(eqn, init);
            % Save results in Solution object
            if length(app.ode_solution) == 1
                app.solution.Value = char(app.ode_solution);
            else
                app.solution.Value = ['[', strjoin(arrayfun(@char, app.ode_solution, 'uniform', 0),', '), ']'];
            end
        end

        % Button pushed function: ClearButton
        function ClearButtonPushed(app, event)
            app.ode.Value = '';
            app.initial_conditions.Value = '';
            app.solution.Value = '';
        end

        % Button pushed function: PlotButton
        function PlotButtonPushed(app, event)
            % Get range
            interval = app.range.Value;
            % Set range
            interval = sscanf(interval, '[%f,%f]');
            % Miscellaneous
            label_x = char(symvar(app.ode_solution));
            % Plot range
            try
                fplot(app.ode_solution, [interval(1), interval(2)], 'LineWidth', 1.2);
                set(gca, 'LineWidth', 1.2, 'FontSize', 14, 'BoxStyle', 'full')
                xlabel(label_x, 'Interpreter', 'latex', 'FontSize', 18);
                ylabel('y', 'Interpreter', 'latex', 'FontSize', 18);
            catch
                message = 'There was an error. Please specify the range as [%f,%f].';
                uialert(app.UIFigure, message, 'Error', 'Icon', 'error');
            end
        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 = [700 400 403 232];
            app.UIFigure.Name = 'MATLAB App';

            % Create GridLayout
            app.GridLayout = uigridlayout(app.UIFigure);
            app.GridLayout.ColumnWidth = {48, 42, 49, 108, 100};
            app.GridLayout.RowHeight = {22, 22, 22, '1x', 22, '1.06x', 22};
            app.GridLayout.ColumnSpacing = 9.33333333333333;
            app.GridLayout.RowSpacing = 11.125;
            app.GridLayout.Padding = [9.33333333333333 11.125 9.33333333333333 11.125];

            % Create CalculateButton
            app.CalculateButton = uibutton(app.GridLayout, 'push');
            app.CalculateButton.ButtonPushedFcn = createCallbackFcn(app, @CalculateButtonPushed, true);
            app.CalculateButton.Layout.Row = 3;
            app.CalculateButton.Layout.Column = 4;
            app.CalculateButton.Text = 'Calculate';

            % Create ClearButton
            app.ClearButton = uibutton(app.GridLayout, 'push');
            app.ClearButton.ButtonPushedFcn = createCallbackFcn(app, @ClearButtonPushed, true);
            app.ClearButton.Layout.Row = 3;
            app.ClearButton.Layout.Column = 5;
            app.ClearButton.Text = 'Clear';

            % Create PlotButton
            app.PlotButton = uibutton(app.GridLayout, 'push');
            app.PlotButton.ButtonPushedFcn = createCallbackFcn(app, @PlotButtonPushed, true);
            app.PlotButton.Layout.Row = 7;
            app.PlotButton.Layout.Column = 5;
            app.PlotButton.Text = 'Plot';

            % Create OrdDifferentialequationLabel
            app.OrdDifferentialequationLabel = uilabel(app.GridLayout);
            app.OrdDifferentialequationLabel.HorizontalAlignment = 'right';
            app.OrdDifferentialequationLabel.Layout.Row = 1;
            app.OrdDifferentialequationLabel.Layout.Column = [1 3];
            app.OrdDifferentialequationLabel.Text = 'Ord. Differential equation';

            % Create ode
            app.ode = uieditfield(app.GridLayout, 'text');
            app.ode.Layout.Row = 1;
            app.ode.Layout.Column = [4 5];
            app.ode.Value = 'D2y+3*Dy+2*y=sin(t)';

            % Create InitialconditionsEditFieldLabel
            app.InitialconditionsEditFieldLabel = uilabel(app.GridLayout);
            app.InitialconditionsEditFieldLabel.HorizontalAlignment = 'right';
            app.InitialconditionsEditFieldLabel.Layout.Row = 2;
            app.InitialconditionsEditFieldLabel.Layout.Column = [2 3];
            app.InitialconditionsEditFieldLabel.Text = 'Initial conditions';

            % Create initial_conditions
            app.initial_conditions = uieditfield(app.GridLayout, 'text');
            app.initial_conditions.Layout.Row = 2;
            app.initial_conditions.Layout.Column = [4 5];
            app.initial_conditions.Value = 'y(0)=0,Dy(0)=0';

            % Create SolutionTextAreaLabel
            app.SolutionTextAreaLabel = uilabel(app.GridLayout);
            app.SolutionTextAreaLabel.HorizontalAlignment = 'right';
            app.SolutionTextAreaLabel.Layout.Row = 5;
            app.SolutionTextAreaLabel.Layout.Column = 3;
            app.SolutionTextAreaLabel.Text = 'Solution';

            % Create solution
            app.solution = uitextarea(app.GridLayout);
            app.solution.Layout.Row = [4 6];
            app.solution.Layout.Column = [4 5];

            % Create RangeEditFieldLabel
            app.RangeEditFieldLabel = uilabel(app.GridLayout);
            app.RangeEditFieldLabel.HorizontalAlignment = 'right';
            app.RangeEditFieldLabel.Layout.Row = 7;
            app.RangeEditFieldLabel.Layout.Column = 3;
            app.RangeEditFieldLabel.Text = 'Range';

            % Create range
            app.range = uieditfield(app.GridLayout, 'text');
            app.range.Layout.Row = 7;
            app.range.Layout.Column = 4;
            app.range.Value = '[0,50]';

            % 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 = example_ODE_ap1

            % 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

[Himalay Baidya]

thank you so much @Alberto Cuadra Lara for you detailed code.I try to follow your code as it is but found a error message only in plotting section.it is saying"Specify a UIAxes handle as first argument."in flot,xlabel,ylabel line.(see below i have attached the error image)also i have share my code.only problem is in plot section rest calculate function works perfectly.

could you kindly tell where is the problem?

thank you in advance.

classdef app2 < matlab.apps.AppBase

    % Properties that correspond to app components
    properties (Access = public)
        UIFigure                matlab.ui.Figure
        OrdDifferentialequationEditFieldLabel  matlab.ui.control.Label
        ode                     matlab.ui.control.EditField
        Initialc
        onditionsEditFieldLabel  matlab.ui.control.Label
        initial_conditions      matlab.ui.control.EditField
        CalculateButton         matlab.ui.control.Button
        ClearButton             matlab.ui.control.Button
        SolutionEditFieldLabel  matlab.ui.control.Label
        solution                matlab.ui.control.EditField
        PlotButton              matlab.ui.control.Button
        RangeEditFieldLabel     matlab.ui.control.Label
        range                   matlab.ui.control.EditField
        UIAxes                  matlab.ui.control.UIAxes
    end


    properties (Access = private)
        ode_solution % Description
    end


    methods (Access = private)

        % Button pushed function: CalculateButton
        function CalculateButtonPushed(app, event)
           
            % Get inputs
            eqn = app.ode.Value;
            init = app.initial_conditions.Value;
            % Solve ODE
            app.ode_solution = dsolve(eqn, init);
            % Save results in Solution object
            if length(app.ode_solution) == 1
                app.solution.Value = char(app.ode_solution);
            else
                app.solution.Value = ['[', strjoin(arrayfun(@char, app.ode_solution, 'uniform', 0),', '), ']'];
            end
       
        end

        % Button pushed function: ClearButton
        function ClearButtonPushed(app, event)
            app.ode.Value = '';
            app.initial_conditions.Value = '';
            app.solution.Value = '';
        end

        % Button pushed function: PlotButton
        function PlotButtonPushed(app, event)
             
         % Get range
            interval = app.range.Value;
            % Set range
            interval = sscanf(interval, '[%f,%f]');
            % Miscellaneous
            label_x = char(symvar(app.ode_solution));
            % Plot range
            try
                fplot(app.ode_solution, [interval(1), interval(2)], 'LineWidth', 1.2);
                set(gca, 'LineWidth', 1.2, 'FontSize', 14, 'BoxStyle', 'full')
                xlabel(label_x, 'Interpreter', 'latex', 'FontSize', 18);
                ylabel('y', 'Interpreter', 'latex', 'FontSize', 18);
            catch
                message = 'There was an error. Please specify the range as [%f,%f].';
                uialert(app.UIFigure, message, 'Error', 'Icon', 'error');
            end
        end
        end
    end

    % App initialization and construction
    methods (Access = private)

        % Create UIFigure and components
        function createComponents(app)

            % Create UIFigure
            app.UIFigure = uifigure;
            app.UIFigure.Position = [100 100 640 480];
            app.UIFigure.Name = 'UI Figure';
            setAutoResize(app, app.UIFigure, true)

            % Create OrdDifferentialequationEditFieldLabel
            app.OrdDifferentialequationEditFieldLabel = uilabel(app.UIFigure);
            app.OrdDifferentialequationEditFieldLabel.HorizontalAlignment = 'right';
            app.OrdDifferentialequationEditFieldLabel.Position = [51 420 141 15];
            app.OrdDifferentialequationEditFieldLabel.Text = 'Ord. Differential equation';

            % Create ode
            app.ode = uieditfield(app.UIFigure, 'text');
            app.ode.Position = [207 416 303 22];

            % Create InitialconditionsEditFieldLabel
            app.InitialconditionsEditFieldLabel = uilabel(app.UIFigure);
            app.InitialconditionsEditFieldLabel.HorizontalAlignment = 'right';
            app.InitialconditionsEditFieldLabel.Position = [102 382 93 15];
            app.InitialconditionsEditFieldLabel.Text = 'Initial conditions';

            % Create initial_conditions
            app.initial_conditions = uieditfield(app.UIFigure, 'text');
            app.initial_conditions.Position = [210 378 300 22];

            % Create CalculateButton
            app.CalculateButton = uibutton(app.UIFigure, 'push');
            app.CalculateButton.ButtonPushedFcn = createCallbackFcn(app, @CalculateButtonPushed, true);
            app.CalculateButton.Position = [232 308 100 22];
            app.CalculateButton.Text = 'Calculate';

            % Create ClearButton
            app.ClearButton = uibutton(app.UIFigure, 'push');
            app.ClearButton.ButtonPushedFcn = createCallbackFcn(app, @ClearButtonPushed, true);
            app.ClearButton.Position = [394 308 100 22];
            app.ClearButton.Text = 'Clear';

            % Create SolutionEditFieldLabel
            app.SolutionEditFieldLabel = uilabel(app.UIFigure);
            app.SolutionEditFieldLabel.HorizontalAlignment = 'right';
            app.SolutionEditFieldLabel.Position = [128 250 50 15];
            app.SolutionEditFieldLabel.Text = 'Solution';

            % Create solution
            app.solution = uieditfield(app.UIFigure, 'text');
            app.solution.Position = [193 135 317 133];

            % Create PlotButton
            app.PlotButton = uibutton(app.UIFigure, 'push');
            app.PlotButton.ButtonPushedFcn = createCallbackFcn(app, @PlotButtonPushed, true);
            app.PlotButton.Position = [395 67 100 22];
            app.PlotButton.Text = 'Plot';

            % Create RangeEditFieldLabel
            app.RangeEditFieldLabel = uilabel(app.UIFigure);
            app.RangeEditFieldLabel.HorizontalAlignment = 'right';
            app.RangeEditFieldLabel.Position = [154 70 42 15];
            app.RangeEditFieldLabel.Text = 'Range';

            % Create range
            app.range = uieditfield(app.UIFigure, 'text');
            app.range.Position = [211 66 100 22];

            % Create UIAxes
            app.UIAxes = uiaxes(app.UIFigure);
            title(app.UIAxes, 'Title');
            xlabel(app.UIAxes, 'X');
            ylabel(app.UIAxes, 'Y');
            app.UIAxes.Position = [296 97 300 185];
        end
    end

    methods (Access = public)

        % Construct app
        function app = app2()

            % Create and configure 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

[Alberto Cuadra Lara]

Hello Himalay,

That is a warning message. It is always recommended to specify the axes object. One option is to include an UIAxes in the app as follows

classdef example_ODE_app < matlab.apps.AppBase

    % Properties that correspond to app components
    properties (Access = public)
        ODEeducationalUIFigure        matlab.ui.Figure
        Panel                         matlab.ui.container.Panel
        ode                           matlab.ui.control.EditField
        OrdDifferentialequationLabel  matlab.ui.control.Label
        initial_conditions            matlab.ui.control.EditField
        InitialconditionsEditFieldLabel  matlab.ui.control.Label
        range                         matlab.ui.control.EditField
        RangeEditFieldLabel           matlab.ui.control.Label
        solution                      matlab.ui.control.TextArea
        SolutionTextAreaLabel         matlab.ui.control.Label
        PlotButton                    matlab.ui.control.Button
        ClearButton                   matlab.ui.control.Button
        CalculateButton               matlab.ui.control.Button
        UIAxes                        matlab.ui.control.UIAxes
    end

    
    properties (Access = private)
        ode_solution % ODE solution [symbolic]
    end
    

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

        % Code that executes after component creation
        function startupFcn(app)
            % Initialize UIAxes
            set(app.UIAxes, 'LineWidth', 1.2, 'FontSize', 14, 'BoxStyle', 'full');
            xlabel(app.UIAxes, '$t$', 'Interpreter', 'latex', 'FontSize', 16);
            ylabel(app.UIAxes, '$y$', 'Interpreter', 'latex', 'FontSize', 16);
        end

        % Button pushed function: CalculateButton
        function CalculateButtonPushed(app, event)
            % Get input string and format to symbolic
            eqn = app.ode.Value;
            init = app.initial_conditions.Value;
            % Solve ODE
            app.ode_solution = dsolve(eqn, init);
            % Save results in Solution object   
            if length(app.ode_solution) == 1
                app.solution.Value = char(app.ode_solution);
            else
                app.solution.Value = ['[', strjoin(arrayfun(@char, app.ode_solution, 'uniform', 0),', '), ']'];
            end
        end

        % Button pushed function: ClearButton
        function ClearButtonPushed(app, event)
            app.ode.Value = '';
            app.initial_conditions.Value = '';
            app.solution.Value = '';
        end

        % Button pushed function: PlotButton
        function PlotButtonPushed(app, event)
            % Get range
            interval = app.range.Value;
            % Set range
            interval = sscanf(interval, '[%f,%f]');
            % Miscellaneous
            label_x = char(symvar(app.ode_solution));
            % Plot range
            try
                fplot(app.UIAxes, app.ode_solution, [interval(1), interval(2)], 'LineWidth', 1.2);
                set(gca, 'LineWidth', 1.2, 'FontSize', 14, 'BoxStyle', 'full')
                xlabel(app.UIAxes, '$t$', 'Interpreter', 'latex', 'FontSize', 16);
                ylabel(app.UIAxes, '$y$', 'Interpreter', 'latex', 'FontSize', 16);
            catch
                message = 'There was an error. Please specify the range as [%f,%f].';
                uialert(app.ODEeducationalUIFigure, message, 'Error', 'Icon', 'error');
            end
        end
    end

    % Component initialization
    methods (Access = private)

        % Create UIFigure and components
        function createComponents(app)

            % Create ODEeducationalUIFigure and hide until all components are created
            app.ODEeducationalUIFigure = uifigure('Visible', 'off');
            app.ODEeducationalUIFigure.Position = [700 400 789 278];
            app.ODEeducationalUIFigure.Name = 'ODE educational';

            % Create UIAxes
            app.UIAxes = uiaxes(app.ODEeducationalUIFigure);
            zlabel(app.UIAxes, 'Z')
            app.UIAxes.FontSize = 14;
            app.UIAxes.Position = [406 10 371 259];

            % Create Panel
            app.Panel = uipanel(app.ODEeducationalUIFigure);
            app.Panel.BorderType = 'none';
            app.Panel.Position = [2 1 397 278];

            % Create CalculateButton
            app.CalculateButton = uibutton(app.Panel, 'push');
            app.CalculateButton.ButtonPushedFcn = createCallbackFcn(app, @CalculateButtonPushed, true);
            app.CalculateButton.Position = [150 186 108 22];
            app.CalculateButton.Text = 'Calculate';

            % Create ClearButton
            app.ClearButton = uibutton(app.Panel, 'push');
            app.ClearButton.ButtonPushedFcn = createCallbackFcn(app, @ClearButtonPushed, true);
            app.ClearButton.Position = [268 186 121 22];
            app.ClearButton.Text = 'Clear';

            % Create PlotButton
            app.PlotButton = uibutton(app.Panel, 'push');
            app.PlotButton.ButtonPushedFcn = createCallbackFcn(app, @PlotButtonPushed, true);
            app.PlotButton.Position = [268 10 121 22];
            app.PlotButton.Text = 'Plot';

            % Create SolutionTextAreaLabel
            app.SolutionTextAreaLabel = uilabel(app.Panel);
            app.SolutionTextAreaLabel.HorizontalAlignment = 'right';
            app.SolutionTextAreaLabel.Position = [92 77 49 67];
            app.SolutionTextAreaLabel.Text = 'Solution';

            % Create solution
            app.solution = uitextarea(app.Panel);
            app.solution.Position = [150 43 239 135];

            % Create RangeEditFieldLabel
            app.RangeEditFieldLabel = uilabel(app.Panel);
            app.RangeEditFieldLabel.HorizontalAlignment = 'right';
            app.RangeEditFieldLabel.Position = [92 10 49 22];
            app.RangeEditFieldLabel.Text = 'Range';

            % Create range
            app.range = uieditfield(app.Panel, 'text');
            app.range.Position = [150 10 108 22];
            app.range.Value = '[0,50]';

            % Create InitialconditionsEditFieldLabel
            app.InitialconditionsEditFieldLabel = uilabel(app.Panel);
            app.InitialconditionsEditFieldLabel.HorizontalAlignment = 'right';
            app.InitialconditionsEditFieldLabel.Position = [31 216 110 22];
            app.InitialconditionsEditFieldLabel.Text = 'Initial conditions';

            % Create initial_conditions
            app.initial_conditions = uieditfield(app.Panel, 'text');
            app.initial_conditions.Position = [150 216 239 22];
            app.initial_conditions.Value = 'y(0)=0,Dy(0)=0';

            % Create OrdDifferentialequationLabel
            app.OrdDifferentialequationLabel = uilabel(app.Panel);
            app.OrdDifferentialequationLabel.HorizontalAlignment = 'right';
            app.OrdDifferentialequationLabel.Position = [-36 247 177 22];
            app.OrdDifferentialequationLabel.Text = 'Ord. Differential equation';

            % Create ode
            app.ode = uieditfield(app.Panel, 'text');
            app.ode.Position = [150 247 239 22];
            app.ode.Value = 'D2y+3*Dy+2*y=sin(t)';

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

    % App creation and deletion
    methods (Access = public)

        % Construct app
        function app = example_ODE_app

            % Create UIFigure and components
            createComponents(app)

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

            % 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.ODEeducationalUIFigure)
        end
    end
end

[Walter Roberson]

                set(gca, 'LineWidth', 1.2, 'FontSize', 14, 'BoxStyle', 'full')

Do not use gca with App Designer. gca applies only to traditional figures.

[Himalay Baidya]

HI @Alberto Cuadra Lara IT SHOWS SOME ERROR .SO I CANT RUN THE EXE. FILE.ERRORS ARE ---

Error using symengine
Unexpected 'identifier'.

Error in mupadengine/evalin_internal (line 113)
                res = mupadmex(statement,output_type{:});

Error in dsolve>mupadDsolve (line 327)
sys = [sys_sym reshape(evalin_internal(symengine, sys_str), 1, [])];

Error in dsolve (line 183)
sol = mupadDsolve(args, options


IN COMMAND WINDOW--
--------------------

 appdesigner
Warning: Support of character vectors and strings will be removed in a future release. Use sym objects to define differential equations
instead. 
Error using symengine
Unexpected 'identifier'.

Error in mupadengine/evalin_internal (line 113)
                res = mupadmex(statement,output_type{:});

Error in dsolve>mupadDsolve (line 327)
sys = [sys_sym reshape(evalin_internal(symengine, sys_str), 1, [])];

Error in dsolve (line 183)
sol = mupadDsolve(args, options);

Error in ODE_Solver/CalculateButtonPushed (line 38)
             app.ode_solution = dsolve(eqn, init);
 
Error using matlab.ui.control.internal.controller.ComponentController/executeUserCallback (line 335)
Error while evaluating Button PrivateButtonPushedFcn.

>>

[Walter Roberson]

There is no documented support for using character vectors for the equations or initial conditions, not since around r2018a or so. And that means that MATLAB is allowed to get confused when you try.