自动化数据抓取技术(IV)：正则表达Regex

任意中文字符

具体请参看

v=c("a","b","c","中","e","文")
    grep("[\\p{Han}]", v, value = T, perl = T)

## [1] "中" "文"

指定出现次数

具体请参看参看

• ?, ?? : 0 or 1 occurrences (?? is lazy, ? is greedy)

• *, *? : any number of occurrences

• +, +? : at least one occurrence

• {n} : exactly n occurrences

• {n,m} : n to m occurrences, inclusive

• {n,m}? : n to m occurences, lazy

• {n,}, {n,}? : at least n occurrence

例子：

To get “exactly N or M”, you need to write the quantified regex twice, unless m,n are special:

X{n,m} if m = n+1
(?:X{n}){1,2} if m = 2n

中文半破折号

通过regex查找替换

(\d{4})-(\d{4})  替换为 \1—\2