手边有一个微博的数据，大体长这个样子：

[data]

uid mid reTweetId reUserId year month

1227341085 3457114435845280 3456570673299700 1154814913 2012 6

1249424622 3457099742503210 3456570673299700 1154814913 2012 6

1619962527 3457285059269340 3456570673299700 1154814913 2012 6

1290180827 3438444762529290 3438423346213440 1207360551 2012 4

1290180827 3460861039707780 3460860292971980 1207360551 2012 6

1249424622 3445158677312120 3444998303654800 1207820500 2012 5

[/data]

我希望可以算出被转发的人(reUserId)每月被转多少次，还有每人每条微博(reTweetId)被另外的同一人(uid)一共被转多少次，呈现在同一个df下：

<br />
mydata1 <- aggregate(mid ~ reUserId + year + month, data = mydata, length)<br />
names(mydata1)[names(mydata1) == 'mid'] <- 'rtMonthly'<br />
mydata2 <- aggregate(mid ~ reUserId + reTweetId + uid, data = mydata, length)<br />
names(mydata2)[names(mydata2) == 'mid'] <- 'rtPerPo'<br />
mydata <- merge(mydata, mydata1, by = c("reUserId", "year", "month")<br />
mydata <- merge(mydata, mydata2, by = c("reUserId", "reTweetId", "uid")<br />

</p>

请问有没有更简短的方式？先前用过Stata，达到同样的效果code大概是这样：

<br />
bys reUserId year month: egen rtMonthly=count(mid)<br />
bys reUserId reTweetId uid: egen rtPerPo=count(mid)<br />

</p>