从名称列中创建一列首字母缩写，作为R中的字符串

下面是我想从中提取大写字母的示例：

df <- data.frame(a = c(1:5), b = c("Words are Here", "Okay", "Be Good Now", "WTF are you Doing", "it's good"))

或使用simplify=FALSE：

[[1]]
[1] "W" "H"

[[2]]
[1] "O"

[[3]]
[1] "B" "G" "N"

[[4]]
[1] "W" "T" "F" "D"

[[5]]
character(0)

我不知道如何使用这两种方法来获得所需的输出，这是一个向量，如：

("WH", "O", "BGN", "WTFD", "")

---

我们可以使用

gsub

匹配一个或多个非大写字符，并将其替换为空白（

“”

）

("WH", "O", "BGN", "WTFD", "")

gsub("[^A-Z]+", "", df$b)
#[1] "WH"   "O"    "BGN"  "WTFD" ""