合并多列，排除空值

我试图弄清楚如何组合多个列，不包括 NA 值。

输入数据框：

data <- data.frame(
  id = c(1:3),
  Item1 = c("Egg", "", ""),
  Item2 = c("Chicken", "Flour", ""),
  Item3 = c("", "", "Bread"),
  Item4 = c("", "Milk", "")
)

所需的数据框：

desired <- data.frame(
  id = c(1:3),
  Item1 = c("Egg", "", ""),
  Item2 = c("Chicken", "Flour", ""),
  Item3 = c("", "", "Bread"),
  Item4 = c("", "Milk", ""),
  Combine = c("Egg, Chicken", "Flour, Milk", "Bread")
)

我尝试使用以下代码组合这些值：

data$Combine = paste(data$Item1, data$Item2, data$Item3, data$Item4, sep=",")

问题是我得到的结果是这样的：

鸡蛋，鸡肉，，
,面粉,牛奶
，，面包，

如果我们使用与OP帖子中类似的方法，请将前导/滞后空格替换为""以及那些有多个重复的,与单个, using gsub

data$Combine <- gsub(",{2,}", ",", 
       gsub("^,+|,+$", "", do.call(paste, c(data[-1], sep=","))))
data$Combine
#[1] "Egg,Chicken" "Flour,Milk"  "Bread"

或者另一种选择是使用paste，删除前导/滞后空格（trimws），然后替换一个或多个空格（\\s+）与一个, using gsub

gsub("\\s+", ",", trimws(do.call(paste,  data[-1])))
#[1] "Egg,Chicken" "Flour,Milk"  "Bread"  

data

data <- structure(list(ID = 1:3, Item1 = c("Egg", "", ""), Item2 = c("Chicken", 
"Flour", ""), Item3 = c("", "", "Bread"), Item4 = c("", "Milk", 
"")), .Names = c("ID", "Item1", "Item2", "Item3", "Item4"),
class = "data.frame", row.names = c(NA, -3L))