r - 如何将 data.frame 解析为树？

Question

这是一个简单的分类(标签和 ID):

test_data <- data.frame(
  cat_id = c(661, 197, 228, 650, 126, 912, 949, 428),
  cat_h1 = c(rep("Animals", 5), rep("Plants", 3)),
  cat_h2 = c(rep("Mammals", 3), rep("Birds", 2), c("Wheat", "Grass", "Other")),
  cat_h3 = c("Dogs", "Dogs", "Other", "Hawks", "Other", rep(NA, 3)),
  cat_h4 = c("Big", "Little", rep(NA, 6)))

解析后的结构应符合以下条件:

list(
  Animals = list(Mammals = list(Dogs  = list(Big = 661, Little = 197), Other = 228),
                 Birds   = list(Hawks = 650, Other = 126)),
  Plants  = list(Wheat = 912, Grass = 949, Other = 428))

Answer 1

如果您对顺序略有变化没有意见，这是一个按列处理的递归解决方案:

f <- function(x, d=cbind(x,NA)) {
    c( 
       # call f by branch
       if(ncol(d) > 3) local({
         x <- d[!is.na(d[[3]]),] 
         by( x[-2], droplevels(x[2]), f, x=NA, simplify=FALSE) 
       }), 
       # leaf nodes
       setNames(as.list(d[[1]]), d[[2]])[is.na(d[[3]])] 
    )
}

这将给出:

> str(f(test_data))
List of 2
 $ Animals:List of 2
  ..$ Birds  :List of 2
  .. ..$ Hawks: num 650
  .. ..$ Other: num 126
  ..$ Mammals:List of 2
  .. ..$ Dogs :List of 2
  .. .. ..$ Big   : num 661
  .. .. ..$ Little: num 197
  .. ..$ Other: num 228
 $ Plants :List of 3
  ..$ Wheat: num 912
  ..$ Grass: num 949
  ..$ Other: num 428