從列表中刪除特定於行的項目

Question

我想創建前3列（'group'，'animal'和'full'）的最後一列（'desired_result'）。以下是可重複使用的示例的代碼。

library(data.table) 
data = data.table(group = c(1,1,1,2,2,2), animal = c('cat', 'dog', 'pig', 'giraffe', 'lion', 'tiger'), desired_result = c('dog, pig', 'cat, pig', 'cat, dog', 'lion, tiger', 'giraffe, tiger', 'giraffe, lion')) 
data[, full := list(list(animal)), by = 'group'] 
data = data[, .(group, animal, full, desired_result)] 

data 
    group animal    full desired_result 
1:  1  cat   cat,dog,pig  dog, pig 
2:  1  dog   cat,dog,pig  cat, pig 
3:  1  pig   cat,dog,pig  cat, dog 
4:  2 giraffe giraffe,lion,tiger lion, tiger 
5:  2 lion giraffe,lion,tiger giraffe, tiger 
6:  2 tiger giraffe,lion,tiger giraffe, lion 

基本上，我想修改'full'，所以它不包含相應的'動物'。我已經嘗試過使用這些列的列表和字符版本的各種lapply命令，但無法解決這個問題。

Answer 1

這裏有一個可能的方法

data[, desired_result := { 
     temp <- unique(unlist(full)) 
     toString(temp[-match(animal, temp)]) 
     }, by = .(group, animal)] 
data 
# group animal    full desired_result 
# 1:  1  cat  cat,dog,pig  dog, pig 
# 2:  1  dog  cat,dog,pig  cat, pig 
# 3:  1  pig  cat,dog,pig  cat, dog 
# 4:  2 giraffe giraffe,lion,tiger lion, tiger 
# 5:  2 lion giraffe,lion,tiger giraffe, tiger 
# 6:  2 tiger giraffe,lion,tiger giraffe, lion 

Answer 2

另一種選擇：

data[, desired := .(Map(setdiff, list(animal), as.list(animal))), by = group] 

#or if starting from full 
data[, desired := .(Map(setdiff, full, animal))] 

（循環魔法使的第一個版本的工作）

Answer 3

我找到了一種方法，以及！

通過將'動物'轉換爲列表，我可以使用mapply。

data$animal = strsplit(data$animal, ' ') 
data$check = mapply(function(x, y) {list(x[x != y]) }, data$full, data$animal) 

data 
group animal    full desired_result   check 
1:  1  cat  cat,dog,pig  dog, pig  dog,pig 
2:  1  dog  cat,dog,pig  cat, pig  cat,pig 
3:  1  pig  cat,dog,pig  cat, dog  cat,dog 
4:  2 giraffe giraffe,lion,tiger lion, tiger lion,tiger 
5:  2 lion giraffe,lion,tiger giraffe, tiger giraffe,tiger 
6:  2 tiger giraffe,lion,tiger giraffe, lion giraffe,lion