how can I define a global variable in app designer?

I have to built an app that read data in .csv file and then display and process them.

[file,path] = uigetfile;
tab=readtable(fullfile(path,file));

I used this code for import and save the data but I don't know how can I set them as 'Global variables'.

Can someone help me ?

[Stephen23]

Why do you need to do that? Using global variables is not recommended for passing data between workpaces, the recommended methods are explained in the MATLAB documentation:

https://www.mathworks.com/help/matlab/creating_guis/share-data-among-callbacks.html

https://www.mathworks.com/help/matlab/creating_guis/share-data-across-callbacks-in-app-designer.html

[Matteo Paolucci]

Thank you !! the second link has been very helpful and now the code runs correctly !

[Kevin Andres Contreras]

¿Me puedes ayudar?

No me quiere copilar

[Matteo Paolucci]

when you have a variable in app designer, it is not saved as when you'd work on command window. If you want use a variable like 'global variable' in app designer you can do this using 'Properties'.

to be clear:

in this following code the variable y can not be 'seen' in other parts of your code. So you have to write app.variablename and write variablename under the part 'Properties' (it is generated automatically).

x = 1:0.1:100;
app.y=cos(x)

in this way you can use your variable every time you want.

so you have to:

1) use app.variablename for variable you want use in other parts of your code. you have to use app.variablename evry time you call it

2) write variablename under the part of code called 'Propeties'

if you have any difficulties you can write me an email

[e-mail]

Answer 1

[Adam Danz]

There are very few reasons, if any, to use global variables in apps and it's usually the sign of trouble.

If the variable is meant to be shared with other functions within the app, declare it as a private variable. If the variable is also needed by external functions or scripts, declare it as a public variable. The link below shows how to do both.

https://www.mathworks.com/help/matlab/creating_guis/share-data-across-callbacks-in-app-designer.html

[Matteo Paolucci]

thank you !

[Josep Llobet]

Thank you so much.

I was using TextLabels and TextArea for save all the App variables... (.-.)

[Chikezie Onyema]

How about loading a very large mat file each time I run app in app designer? How can you not spend minutes loading a file if you have to run the program each time during coding and testing?

[Stephen23]

"How can you not spend minutes loading a file if you have to run the program each time during coding and testing?"

Some approaches:

• Import the data beforehand and supply the file data when you call the program.
• Store it in memory for next time: https://www.mathworks.com/help/matlab/ref/persistent.html
• Avoid loading it into memory: https://www.mathworks.com/help/matlab/large-files-and-big-data.html