from MATLAB command line , when I type my variable a , it gives me values as expected :
a =
value_1
value_2
and I wou
How are you reading in the xml file? If you're using xmlread then MatLab adds a lot of white space in there for you and could be the cause of your problems.
http://www.mathworks.com/matlabcentral/fileexchange/28518-xml2struct
This will put your xml file into a struct where you should be able to access the elements in the array.