如何基于一组不等式约束对data.table进行排序?

library(igraph)
g = ineqs[, graph_from_edgelist(cbind(X,Y), directed=TRUE)]
o = names(topo_sort(g))

dt[, v := factor(Foo, levels = o, ordered=TRUE)]
dt[order(v)]


    Foo    v
 1:   x    x
 2:   g    g
 3:   o    o
 4:   y    y
 5:   q    q
 6:   b    b
 7:   m    m
 8:   f    f
 9:   r    r
10:   s    s
11:   j    j
12:   u    u
13:   z    z
14:   e    e
15:   a <NA>
16:   c <NA>
17:   d <NA>
18:   h <NA>
19:   i <NA>
20:   k <NA>
21:   l <NA>
22:   n <NA>
23:   p <NA>
24:   t <NA>
25:   v <NA>
26:   w <NA>
    Foo    v

所有不在 ineqs 被分类到最后。

topo_sort . 这就告诉你你的任务没有很好的定义 .

我举个例子。考虑条件

    X Rel Y
1: x   < b
2: g   < f

各种命令是可以想象的

        x < g < f < b
g     < x     <     b   <   f
g     < x     < f < b
g < f < x         < b
        x < g <     b     < f
        x <         b < g < f

所有这些都满足前两条线所列的条件。

以下是我的结果:

1. 首先,我们定义四个字母并使用 gtools::permutations .

   char <- c("b", "f", "g", "x")
   
   library(gtools)
   perm <- as.data.frame(permutations(length(char), length(char), char))
   

   有24种可能的排列。

2. df <- read.table(text =
       "X Rel Y
   x   < b
   g   < f", header = T)
   
   # Convert factors to character vectors
   df[] <- sapply(df, as.character)
   

3. 我们现在循环抛出置换和成对条件,并标记置换数据中不满足任何成对条件的行。

   rmv <- c()
   for (i in 1:nrow(perm)) {
       # Here we loop throw all possible permutations and eliminate those that
       # do not fulfil the pairwise conditions
       for (j in 1:nrow(df)) {
           # Here we loop throw the pairwise conditions
           cond <- eval(parse(text = sprintf("`%s`", df[j, "Rel"])))(
               which(perm[i, ] == df[j, "X"]),
               which(perm[i, ] == df[j, "Y"]))
           if (cond == FALSE) {
               rmv <- c(rmv, i)
               break
           }
       }
   }
   

4. 剩下的满足条件的排列是

   perm[-rmv, ]
   #   V1 V2 V3 V4
   #16  g  f  x  b
   #17  g  x  b  f
   #18  g  x  f  b
   #20  x  b  g  f
   #23  x  g  b  f
   #24  x  g  f  b