【每天一个R语言命令】-substr

【描述】

Extract or replace substrings in a character vector.
提取或取代字符串中的子字符串

【用法】

substr(x, start, stop)
substring(text, first, last = 1000000L)
substr(x, start, stop) <- value
substring(text, first, last = 1000000L) <- value

【参数】

x, text 
a character vector.

start, first    
integer. The first element to be replaced.

stop, last  
integer. The last element to be replaced.

value   
a character vector, recycled if necessary.

【代码】

> substr(month.name, 1, 3)
 [1] "Jan" "Feb" "Mar" "Apr" "May" "Jun" "Jul" "Aug" "Sep" "Oct" "Nov" "Dec"
> paste(substr(month.name, 1, 3), '.', sep = '')
 [1] "Jan." "Feb." "Mar." "Apr." "May." "Jun." "Jul." "Aug." "Sep." "Oct." "Nov." "Dec."