R：构建条件组合

我正在寻找一种有效的方法来构建具有大量条件组合的数据帧。我试图将这个过程转化为某种“创建df”灵活的功能，其工作原理如下：

# STEP 1
level.1 <- c("Netherlands", "New Zealand", "Europe")

# STEP 2: 
level.1 <- c("Netherlands", "New Zealand", "Europe", "Europe")
level.2 <- c(NA, NA, "London", "Paris")
df <- data.frame(level.1, level.2)
df

# STEP 3:
level.1 <- c("Netherlands", "New Zealand", "Europe", "Europe", "Europe", "Europe")
level.2 <- c(NA, NA, "London", "London", "Paris", "Paris")
level.3 <- c(NA, NA, "City", "Roads", "City", "Roads")
data.frame(level.1, level.2, level.3)

# STEP 4:
level.1 <- c("Netherlands", "New Zealand", "Europe", "Europe", "Europe", "Europe", "Europe", "Europe")
level.2 <- c(NA, NA, "London", "London", "London", "London", "Paris", "Paris")
level.3 <- c(NA, NA, "City", "City", "Roads", "Roads", "City", "Roads")
level.4 <- c(NA, NA, "A-Regulated", "G-Regulated", "A-Regulated", "G-Regulated", NA, NA)
data.frame(level.1, level.2, level.3, level.4)

#步骤1
level.1您可以通过使用merge来实现这一点，并将其简化为循环

在每个级别，您将只需要指定要加入的值：

level.1 <- data.frame(country = c("Netherlands", "New Zealand", "Europe"))
level.2 <- data.frame(country = c("Europe"), city = c('paris','london' ))
level.3 <- data.frame(country = c('Europe'), location = c('city', 'roads'))
level.4 <- data.frame(country = c('Europe'), regulation = c("A-Regulated", "G-Regulated", "C-Regulated"))

level.1 <- data.frame(country = c("Netherlands", "New Zealand", "Europe"))
level.2 <- data.frame(country = c("Europe"), city = c('paris','london' ))
level.3 <- data.frame(country = c('Europe'), location = c('city', 'roads'))
level.4 <- data.frame(country = c('Europe'), regulation = c("A-Regulated", "G-Regulated", "C-Regulated"))

Reduce(function(x, y) merge(x, y, all=TRUE), list(level.1, level.2, level.3, level.4))

       country   city location  regulation
1       Europe  paris     city A-Regulated
2       Europe  paris     city G-Regulated
3       Europe  paris     city C-Regulated
4       Europe  paris    roads A-Regulated
5       Europe  paris    roads G-Regulated
6       Europe  paris    roads C-Regulated
7       Europe london     city A-Regulated
8       Europe london     city G-Regulated
9       Europe london     city C-Regulated
10      Europe london    roads A-Regulated
11      Europe london    roads G-Regulated
12      Europe london    roads C-Regulated
13 Netherlands   <NA>     <NA>        <NA>
14 New Zealand   <NA>     <NA>        <NA>

merge(merge(merge(level.1, level.2, all = TRUE), level.3, all = TRUE), level.4, all = TRUE)