在R中，我如何将字符与字符串中的“”分隔开？

Question

我有一个字符串列表，我希望将列表中每个元素的第一个字符作为子集。例如，我只想在列表的第一个元素中获得"Apr 2017"，而不是"Apr 2017" "masked" "idw2"。

有什么想法吗？

> idwstr
[[1]]
[1] "Apr 2017" "masked"   "idw2"    

[[2]]
[1] "Aug 2017" "masked"   "idw2"    

[[3]]
[1] "Dec 2017" "masked"   "idw2"    

[[4]]
[1] "Feb 2017" "masked"   "idw2"    

[[5]]
[1] "Jan 2017" "masked"   "idw2"    

[[6]]
[1] "Jul 2017" "masked"   "idw2"    

[[7]]
[1] "Jun 2017" "masked"   "idw2"    

[[8]]
[1] "Mar 2017" "masked"   "idw2"    

[[9]]
[1] "May 2017" "masked"   "idw2"    

[[10]]
[1] "Nov 2017" "masked"   "idw2"    

[[11]]
[1] "Oct 2017" "masked"   "idw2"    

[[12]]
[1] "Sep 2017" "masked"   "idw2"    

> idwstr[[1]]
[1] "Apr 2017" "masked"   "idw2"```

Answer 1

若要选择列表中每个向量的第一个元素，需要将函数[应用于具有参数1的列表的每个元素。

sapply(idwstr, '[', 1)