Cris - from your code it appears that you are trying to create a variable called A1 as
and do the same for A2 and A3. Is this the case? While you can do this using such functions as sprintf and eval, this isn't recommended because of the challenges in debugging the code when errors appear (among other reasons).
Instead, just create one matrix A which is built from the the three vectors, and then add 6 to it. Something like
A = [data1 ; data2 ; data3];
A = A +6;
Try the above and see what happens!