合并数据框只保留一个观察值答案

【问题标题】：merge data frame only keep one observation合并数据框只保留一个观察值
【发布时间】：2015-03-01 14:57:30
【问题描述】：

我有两个数据框：客人和地址。

“guests”包含人名和相应的人级数据。人们按家庭 ID 进行组织，这样同一个家庭中的多个人共享一个家庭 ID，如下所示：

## Guests data frame looks like this:
Family.ID <- c(1,1,1,2,2,3,3,3,4,4)
Names <- c("Person_A", "Person_B", "Person_C", "Person_D", "Person_E",
           "Person_F", "Person_G", "Person_H", "Person_I", "Person_J")
list <- c("A", "A", "A", "A", "A", "B", "B", "B", "C", "C")
guests <- data.frame(Family.ID, Names, list)

“addresses”包含家庭及其地址，也由家庭 ID 标记，如下所示：

## Addresses data frame looks like this:
family <- c("Person A, B, & C", "Person D & E", "Person F, G, & H", "Person I & J")
ID <- c(1,2,3,4)
address <- c("family 1's address", "family 2's address", "family 3's address", "family 4's address")
addresses <- data.frame(ID, family, address)
names(addresses) <- c("Family.ID", "Family", "Address")

我的目标是将变量 guest$list 添加到“addresses”中。我尝试像这样合并“guests”和“addresses”：

both <- merge(guests, addresses, by = "Family.ID")

从合并中，我得到：

  Family.ID Names     list  Family              Address
        1   Person_A    A   Person A, B, & C    family 1's address
        1   Person_B    A   Person A, B, & C    family 1's address
        1   Person_C    A   Person A, B, & C    family 1's address
        2   Person_D    A   Person D & E        family 2's address
        2   Person_E    A   Person D & E        family 2's address
        3   Person_F    B   Person F, G, & H    family 3's address
        3   Person_G    B   Person F, G, & H    family 3's address
        3   Person_H    B   Person F, G, & H    family 3's address
        4   Person_I    C   Person I & J        family 4's address
        4   Person_J    C   Person I & J        family 4's address

但我想得到的只是将“列表”添加到“地址”中，如下所示：

  Family.ID Family              Address             List
        1   Person A, B, & C    family 1's address  A
        2   Person D & E        family 2's address  A
        3   Person F, G, & H    family 3's address  B
        4   Person I & J        family 4's address  C

在合并之前我需要做一些事情来重塑数据框吗？

【问题讨论】：

试试unique 即。 unique(both[-2])
或者只是merge(unique(guests[-2]), addresses, by='Family.ID') -2 是删除第二列Names，它没有显示在预期的输出中
谢谢！那行得通。

标签： r merge

【解决方案1】：

您可以在删除Names 列（guests[-2]）后将merge 与unique 行的“guests”数据行（guests[-2]）

merge(unique(guests[-2]), addresses, by='Family.ID')
#   Family.ID list           Family            Address
#1         1    A Person A, B, & C family 1's address
#2         2    A     Person D & E family 2's address
#3         3    B Person F, G, & H family 3's address
#4         4    C     Person I & J family 4's address

【讨论】：