在数据框中以数字方式对因子进行重新排序

Question

我有从0到39的因子。这是它们现在的订购方式:

> levels(items$label)
 [1] "0"  "1"  "10" "11" "12" "13" "14" "15" "16" "17" "18" "19"
[13] "2"  "20" "21" "22" "23" "24" "25" "26" "27" "28" "29" "3" 
[25] "30" "31" "32" "33" "34" "35" "36" "37" "38" "39" "4"  "5" 
[37] "6"  "7"  "8"  "9"

如何出于显示目的按数字顺序对其重新排序？我不想更改数据框的含义。

更新:如何使用排序后的因子 items更新原始数据帧 labels？这不应实质性地更改数据帧；我只希望这些因素在后续操作中以正确的顺序出现。

Answer 1

sorted_labels <- paste(sort(as.integer(levels(items$label))))

给出:

 [1] "0"  "1"  "2"  "3"  "4"  "5"  "6"  "7"  "8"  "9"  "10" "11"
[13] "12" "13" "14" "15" "16" "17" "18" "19" "20" "21" "22" "23"
[25] "24" "25" "26" "27" "28" "29" "30" "31" "32" "33" "34" "35"
[37] "36" "37" "38" "39"

或者(如 https://stackoverflow.com/a/15665655/109618中所述):

sorted_labels <- order(levels(items$label)) - 1
# order by itself is a 1-based vector
# using `- 1` gives a 0-based vector

根据更新的问题，这将更新数据框:

items$label <- factor(items$label, levels = sorted_labels)