Well, it looks like your code needs interaction with user when using listdlg.
It is obvious that a choice should be made before executing your fourth code line. Otherwise, you won't have any value for indx.
You should wait for user's choice and then walk through the rest of your code.
Also, it makes no sense using numel(indx), as indx is a value alone. It doesn't return an array or something to get the number of elements.
The second argument of listdlg says about the user clicked the ok button, or double-clicked your item in your list.
1 if clicked, 0 if clicked esc or closed the window.
So, I don't know what you want to do after the fourth line, but in order to make indx appear in your workspace, do this:
display ('Please enter PRODUCTS you would like to consider: ') ;
list = {'Meat','Dairy','Frozen','Ice Cream','Produce'};
[indx,tf] = listdlg('ListString',list);
if tf == 1
indx
end
If that helps, please accept the answer.
Cheers.
