regex - 从字符串向量中提取数字

Question

我有这样的字符串:

years<-c("20 years old", "1 years old")

我只想 grep 来自该向量的数字。预期输出是一个向量:

c(20, 1)

我该如何去做呢？

Answer 1

怎么样

# pattern is by finding a set of numbers in the start and capturing them
as.numeric(gsub("([0-9]+).*$", "\\1", years))

或

# pattern is to just remove _years_old
as.numeric(gsub(" years old", "", years))

或

# split by space, get the element in first index
as.numeric(sapply(strsplit(years, " "), "[[", 1))