一个旁门左道方法，可以找出相同的行。
<br />
a <- matrix(c(1:9,7:9), byrow = T, ncol = 3)<br />
b <- matrix(4:12,byrow = T, ncol = 3)<br />
c <- matrix(7:15,byrow = T, ncol = 3)<br />
d <- unique(merge(a,merge(b,c))); d ##相同的行<br />
测试一下速度，似乎还不错:)
<br />
a2 <- matrix(sample(1:5, 80000, re=T), byrow = T, ncol = 8)<br />
b2 <- matrix(sample(1:5, 80000, re=T), byrow = T, ncol = 8)<br />
c2 <- matrix(sample(1:5, 80000, re=T), byrow = T, ncol = 8)<br />
system.time(d2 <- unique(merge(a2,merge(b2,c2))))<br />
##结果<br />
user system elapsed <br />
0.25 0.00 0.25 <br />
