plot

Dear R users:

C1

time        X1
1   0.5  6.296625
2   1.0 10.283977
3   1.5 12.718610
4   2.0 14.112740
5   3.0 15.053917
6   4.0 14.739725
7   6.0 12.912230
8   8.0 10.893264
9   0.5  6.289166
10  1.0 10.251247
11  1.5 12.651346
12  2.0 14.006958
13  3.0 14.870618
14  4.0 14.487026
15  6.0 12.555566
16  8.0 10.474695

plot(C1,type="l")

In the plot, there is a straight line between time=0.5 and time=8,
If I do not want the straight line, what should I do?
Thanks for any help!!