A few things:
First, try to avoid using i as a variable, because by default in Matlab i = sqrt(-1). I'm going to switch your i to n.
As you've set up your loop, k and i will always be the same. Why not just use,
for n = 1:10:30
(commands)
end
If you need to run the loop for n = 1:30 (the same thing as n = 1:1:30), but you want to do some special commands when n = 1, 11, and 21, consider using mod.
for n = 1:10:30
(commands)
if mod(n,10)==1
(do something fancy)
end
end
