> data(state)
> state.name[47:50]
[1] "Washington" "West Virginia" "Wisconsin" "Wyoming

·

> substring(state.name[47:50], first=3, last=1000)

[1] "shington" "st Virginia" "sconsin" "oming"

>

> substring(state.name[47:50], first=3, last=1000)<-"BBB"

> state.name[47:50]

[1] "WaBBBngton" "WeBBBVirginia" "WiBBBnsin" "WyBBBng

这里1000 表示什么意思？