Pass variable to .m file from app designer

I am new in matlab app designer, but I have gone through basics of it. I have a very simple query where I am stuck at.

I am calling "backtest.m" file in app designer

%backtest.m file
clc;
clear;
close all;

z = x + 6;

And this is the app designer code

    methods (Access = private)

        % Button pushed function: Button
        function ButtonPushed(app, event)
            x = app.xEditField.Value;
            backtest;
        end
    end

I get an error where x is undefined. What should I do to remove this error?

Thanks in advance.

Prabhjeet

[Yongjian Feng]

Your .m shall be a function:

function backtest(x)
    z = x + 6;
end

Then call it as backtest(x) from app designer.

[prabhjeet singh]

Thank you very much for the prompt response. I did exactly the same but now I am getting different error. Probably matlab does not like me.

Now the function file is (name of file is also backtest)

function backtest(x)
z = x + 6;
end

And code in app designer is as follows

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

        % Button pushed function: Button
        function ButtonPushed(app, event)
           %global xx;
            x = app.xEditField.Value;
            backtest(x);
            app.zEditField.value = z;
        end
        end

z should show the final value from backtest.m file in app design view.

Sorry for troubling again.

Thanks,

Prabhjeet

[Yongjian Feng]

Please check my answer below.

Answer 1

[Yongjian Feng]

Return z value from your funciton backtest.m:

function z = backtest(x)
    z = x + 6;
end

Call this function from app designer like this:

z = backtest(x);

Basically you shall pass input/output to/from your function using input argument and return. Don't pass data using global variables.

[prabhjeet singh]

Once again thank you for instant response. I tried both the methods (Feng and Cris suggestions in this thread). But, unfortunately I still couldnt figure out this simple problem which I have made complex..

PFA screenshot of the new error which I am getting now.

Sorry for the trouble again.

[Yongjian Feng]

Your function doesn't return anything. Change your function to

function z=backtest(x)
    z=x+6;
end

Pay attention to the first line.

[prabhjeet singh]

Thank you for your answer. Now I get different error after paying attention to the first line.

Attempt to execute SCRIPT backtest as a function:

C:\Users\...\backtest.m

[Yongjian Feng]

You might have two copies of backtest.m. One is just a script, the other is a function.

Try

which -all backtest

Get rid of the script and keep the function.

[prabhjeet singh]

Thank you for the prompt response. Unfortunately, it did not work again. However, I found the solution by defining variables in public property. Now it is working the way it should.

Thank you once again for your responses.

Thanks,

Prabhjeet

[Ayman Shaban]

Thank you very much for your answer, i have another Q , how can i show the result of .m file on app designer after already calling the .m file

Answer 2

[Cris LaPierre]

This will never work as written. The clear inside the m-file, whether a script or function, will remove any variables, including the one passed in.

Remove the following from your m-file

clc;
clear;
close all;

Place the m-file in the same folder as your app. Now when you call it, it's the same as adding the code from your m-file to the code in the callback function.

Note that the variable z will only exist inside the callback function. You need to keep in mind your variable scope.

I do agree that turning this into a function makes more programatic sense to me, but it is not necessary to get it to work.