比較 R 中的兩個表，找出客戶沒有購買的產品

Question

我有兩個表如下：

Cust_list <- data.frame(
stringsAsFactors = FALSE,
Customer = c("Mike S.","Tim P."),
Type = c("Shoes","Socks"),
Product_ID = c(233,6546)
)


Product_Table <- data.frame(
stringsAsFactors = FALSE,
Product_ID = c(233,256,296,8536,6546,8946),
Type = c("Shoes","Shoes","Shoes", "Socks","Socks","Socks")
)

我正在尋找識別“客戶”未在“類型”中購買的“產品 ID”。

例如，Mike S. 在“Shoes”下購買了 Product ID =“233”和 Type =“Shoes”，但沒有購買 Product ID =“256”和“296”。 由於 Mike S. 沒有購買 Type = "Socks"，這不會包含在 output 中。

Output 表如下。

Answer 1

select(Cust_list, -Product_ID) %>%
  left_join(Product_Table, 'Type')%>%
  anti_join(Cust_list)

 Customer  Type Product_ID
1  Mike S. Shoes        256
2  Mike S. Shoes        296
3   Tim P. Socks       8536
4   Tim P. Socks       8946

Answer 2

這是否有效：

library(dplyr)
library(tidyr)
Cust_list %>% full_join(Product_Table) %>% arrange(Type) %>% 
           fill(Customer,.direction = 'down') %>% anti_join(Cust_list)
Joining, by = c("Type", "Product_ID")
Joining, by = c("Customer", "Type", "Product_ID")
  Customer  Type Product_ID
1  Mike S. Shoes        256
2  Mike S. Shoes        296
3   Tim P. Socks       8536
4   Tim P. Socks       8946