Dominika - why is one variable named mape but then you reference mape_2 where you set the string of the text10 control? If you are trying to update the text string with a combination of 'MAPE =' and 50 then try doing the following
mape = 50;
set(handles.text10, 'String', ['MAPE = ' num2str(mape)]);
In the above, we use num2str to convert the number into a string and then concatenate it with 'MAPE =' using the square brackets.
