<br />
> x1=c(1.1,2.2,3.3,4.4,5,6,7)<br />
> x1<br />
[1] 1.1 2.2 3.3 4.4 5.0 6.0 7.0<br />
> x1[which(x1==c(6.0,7.0))]<br />
numeric(0)<br />
Warning message:<br />
In x1 == c(6, 7) :<br />
longer object length is not a multiple of shorter object length<br />
</p>
这是什么原因？
