Combine multiple columns, excluding null values

问题

I'm trying to figure out how to combine multiple columns, excluding NA values.

Input dataframe:

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

Desired dataframe:

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")
)

I have tried combining the values using the following code:

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

The issue is that I'm getting results like this:

Egg,Chicken,,
,Flour,,Milk
,,Bread,

回答1:

If we use the similar approach as in the OP's post, replace the leading/lagging spaces with "" and those having more than one repeating , with a single , using gsub

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

Or another option is to use paste, remove the leading/lagging spaces (trimws) and then replace one or more spaces (\\s+) with a , 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))

回答2:

Adding ", " for non-empty values.

data1 <- sapply(data[-1], function(x) ifelse(x != "", paste(x, " ", sep = ","), ""))

data1 <- data.frame(id = c(1:3), data1)

Creating the new column.

data$Combine <- paste0(data1$Item1, data1$Item2, data1$Item3, data1$Item4)

Cutting the last symbols.

data$Combine <- sapply(data$Combine, function(t) substr(t, 1, nchar(t)-2))
data

来源：https://stackoverflow.com/questions/41523123/combine-multiple-columns-excluding-null-values

标签

concatenation