In appdesigner, how do I reference a variable I just defined generally?

Hi, in app designer I followed this procedure:

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

In my case T is a table. After defining it I also want to parse it a little and create sub variables based on data in T. I found out that this is tricky... When I try running the following code, I get an error:

Undefined function or variable 'T'.

If I try app.T - I get the same error.

So - how do I reference T?

    properties (Access = public)
        T = readtable('All_proteins_summary.csv'); % get data
        H = height(T) % also tried app.T --> also soesn't work
    end

[Geoff Hayes]

Iddo - where are you observing the error Undefined function or variable 'T'? In the above properties code or in a callback? I think you need to do the parsing elsewhere like in the StartupFcn instead. The properties block may just be for defining and initializing properties.

[Iddo Weiner]

Good question, sorry I didn't make it clear enough.

I'm observing this error within the properties code.