我们可能需要do.call

library(data.table)
data[, combinations := do.call(paste, c(.SD, sep = ", ")), .SDcols = 4:ncols]

• 输出

> data
   id number day apple orange banana        combinations
1:  1     35   2   red orange yellow red, orange, yellow
2:  2     12   3   red   <NA> yellow     red, NA, yellow
3:  3     47   5  <NA> orange yellow  NA, orange, yellow

或者使用unite，它可以使用na.rm = TRUE删除NA元素

library(dplyr)
library(tidyr)
data %>% 
  unite(combinations, all_of(4:ncols), sep = ", ", na.rm = TRUE, remove = FALSE)

• 输出

id number day        combinations apple orange banana
1:  1     35   2 red, orange, yellow   red orange yellow
2:  2     12   3         red, yellow   red   <NA> yellow
3:  3     47   5      orange, yellow  <NA> orange yellow

数据

data <- structure(list(id = 1:3, number = c(35L, 12L, 47L), day = c(2L, 
3L, 5L), apple = c("red", "red", NA), orange = c("orange", NA, 
"orange"), banana = c("yellow", "yellow", "yellow")), 
class = "data.frame", row.names = c(NA, 
-3L))
setDT(data)

使用dplyr，使用rowwise

library(dplyr)

df %>% 
  rowwise() %>% 
  mutate(combinations = list(c_across(4:ncol({{df}})))) %>% 
  data.frame()
  id number day apple orange banana        combinations
1  1     35   2   red orange yellow red, orange, yellow
2  2     12   3   red   <NA> yellow     red, NA, yellow
3  3     47   5  <NA> orange yellow  NA, orange, yellow

数据

df <- structure(list(id = 1:3, number = c(35L, 12L, 47L), day = c(2L, 
3L, 5L), apple = c("red", "red", NA), orange = c("orange", NA, 
"orange"), banana = c("yellow", "yellow", "yellow")), class = "data.frame", row.names = c(NA, 
-3L))