为可变级别组合的每个实例创建一个“实例编号”[重复]答案

【问题标题】：Create an "instance number" for each instance of a combination of variable levels [duplicate]为可变级别组合的每个实例创建一个“实例编号”[重复]
【发布时间】：2020-07-15 21:30:17
【问题描述】：

我需要计算每个变量组合的实例数，并将其转换为新变量。例如，

set.seed(2)
V1 <- sample(rep(c(1:3),10))
V2 <- rep_len(c("small", "large"),30)
temp <- cbind(V1,V2)

产生一个数据框，其前十行如下所示：

       V1  V2     
 [1,] "3" "small"
 [2,] "3" "large"
 [3,] "3" "small"
 [4,] "1" "large"
 [5,] "2" "small"
 [6,] "2" "large"
 [7,] "1" "small"
 [8,] "3" "large"
 [9,] "3" "small"
[10,] "3" "large"

我需要一个新变量，它可以计算到目前为止该变量组合在数据框中出现的次数。结果应该类似于：

       V1  V2      V3 
 [1,] "3" "small" "1"
 [2,] "3" "large" "1"
 [3,] "3" "small" "2"
 [4,] "1" "large" "1"
 [5,] "2" "small" "1"
 [6,] "2" "large" "1"
 [7,] "1" "small" "1"
 [8,] "3" "large" "2"
 [9,] "3" "small" "3"
[10,] "3" "large" "3"

什么是执行此操作的有效方法？（我不一定需要它们是字符向量；我只需要一个通用的解决方案。）

【问题讨论】：

您创建的输入数据和显示的数据不正确
@akrun，已修复。谢谢。

标签： r dataframe recode

【解决方案1】：

我们可以在转换为data.frame后按'V1'，'V2'分组，然后创建新列作为row_number()的行序列

library(dplyr)
as.data.frame(temp) %>%
      group_by(V1, V2) %>%
      mutate(V3 = row_number())

数据

temp <- structure(list(V1 = c(3L, 3L, 3L, 1L, 2L, 2L, 1L, 3L, 3L, 3L), 
    V2 = c("small", "large", "small", "large", "small", "large", 
    "small", "large", "small", "large")), class = "data.frame", 
    row.names = c(NA, 
-10L))

【讨论】：