将嵌套的 data.frame 转换为分层列表 [英] Convert nested data.frame to a hierarchical list

问题描述

有没有一种巧妙的方法可以将嵌套的 data.frame 转换为分层列表?

Is there a neat way to convert a nested data.frame to a hierarchical list?

我在下面使用 for 循环来完成它，但理想情况下有一个更简洁的解决方案，可以推广到任意数量的嵌套列.

I do it below with a for loop, but ideally there is a neater solution that generalizes to an arbitrary number of nested columns.

nested_df <- expand.grid(V1 = c('a','b','c'),
                         V2 = c('z','y'))%>%
    group_by_all()%>%
    do(x=runif(10))%>%
    ungroup

nested_ls <- list()
for(v1 in unique(nested_df$V1)){
    for(v2 in unique(nested_df$V2)){
        nested_ls[[v1]][[v2]] <- nested_df%>%
            filter(V1==v1 & V2==v2)%>%
            pull(x)%>%
            unlist
    }
}

str(nested_ls)

推荐答案

如果你对z和y这两个名字不是很严格，也可以用[[1]] 和[[2]]，那么就可以直接做，

If you are not very strict with the names z and y, and can also work with [[1]] and [[2]], then you can directly do,

split(nested_df$x, nested_df$V1)

如果你需要名字，那么

lapply(split(nested_df, nested_df$V1), function(i)split(i$x, i$V2))

#Or as @Frank mentions in comments, we can use setNames
lapply(split(nested_df, nested_df$V1), function(i) setNames(i$x, i$V2))

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