[qingtian]

for n=1:1:21
if 7<=n&n<=12
A(n)=B(n)
end
end
plot(t,A)

A =

Columns 1 through 12

0 0 0 0 0 0 8 8 8 8 8 8

Columns 13 through 21

8 0 0 0 0 0 0 0 0