请教filter

xxzhiyouwo

x=1:5
> filter(x,rep(1,2),"r")
Time Series:
Start = 1
End = 5
Frequency = 1
[1]  1  3  7 14 26
> x=1:5
> filter(x,rep(1,1),"r")
Time Series:
Start = 1
End = 5
Frequency = 1
[1]  1  3  6 10 15
请教上面的计算过程是？R里面的解释没有看懂。谢谢！