从字符串中提取世纪和年份

Question

I have a large column displaying a string such as:

20-1843PA-HY-4563-214DF

The "20" is the century while the "18 is the year. What is the simplest way to extract these two using a function and have an output of 2018 in R?

Answer 1

We can use sub to capture the digits as a group from the start ( ^ ) of the string followed by the - , then capture the two digits ( (\\d{2}) ) and replace with the backreference ( \\1\\2 ) of the captured group

f1 <- function(nm) as.numeric(sub("^(\\d+)-(\\d{2}).*", "\\1\\2", nm))
f1(str1)
#[1] 2018

data

str1 <- "20-1843PA-HY-4563-214DF"

Answer 2

I would do something like this:

chr_collumn<-"20-1843PA-HY-4563-214DF"
chr_collumn<-strsplit(chr_collumn,"-")
chr_collumn<-unlist(chr_collumn)[1:2]
chr_year<-paste0(chr_collumn[1],strtrim(chr_collumn[2],width=2))
chr_year<-as.numeric(chr_year)
chr_year