r - 删除 NA 并使用牛津逗号的跨列串联

Question

我想实现跨列的串联，删除 NA 并观察牛津逗号。

    x <-  data.frame(ID = 1:3,
                 col1 = c("snap", "snap", NA),
                 col2 = c(NA, "crackle", "crackle"),
                 col3 = c(NA, NA, "pop"),
                 col4 = c(NA, "yummy", NA))

我想使用上面的数据框连接 col1:col4 并将结果返回给 x$treats

x$treats[1]
    "snap"

x$treats[2]
"snap, crackle, and yummy" 

x$treats[3]
"crackle and pop"

数据集还有一个不应包含在串联中的 ID 变量(因此不允许我指定所需列的解决方案是不完整的)。

Answer 1

这是另一种选择，尽管要冗长得多。通过将列表生成包装到一个函数中，如果需要，我们还可以添加一个选项来禁用牛津逗号:

x <-  data.frame(
  ID = 1:3,
  col1 = c("snap", "snap", NA),
  col2 = c(NA, "crackle", "crackle"),
  col3 = c(NA, NA, "pop"),
  col4 = c(NA, "yummy", NA)
)

language_list <- function(x, oxford_comma = TRUE) {
  x <- x[!is.na(x)]

  if (length(x) < 2) {
    return(x)
  }

  last <- tail(x, 1)
  rest <- head(x, -1)

  if (length(rest) == 1) {
    return(paste(rest, "and", last))
  }

  rest <- paste(rest, collapse = ", ")    
  paste0(rest, if (oxford_comma) ",", " and ", last)
}

cols <- paste0("col", 1:4)
x$treats <- apply(x[, cols], 1, language_list) 

x$treats                                            
#> [1] "snap"                     "snap, crackle, and yummy"
#> [3] "crackle and pop"