如何将分层数据集转换为R中的正常数据集

install.packages("reshape2")
library(reshape2)

data <- data.frame(ID = 1:5,
                   Name = c("Alice", "Bob", "Charlie", "David", "Eve"),
                   Age = c(25, 30, 35, 40, 45),
                   Group1_Var1 = c(1, 2, 3, 4, 5),
                   Group1_Var2 = c(6, 7, 8, 9, 10),
                   Group2_Var1 = c(11, 12, 13, 14, 15),
                   Group2_Var2 = c(16, 17, 18, 19, 20))

melted_data <- melt(data, id.vars = c("ID", "Name", "Age"), measure.vars = c("Group1_Var1", "Group1_Var2", "Group2_Var1", "Group2_Var2"))

print(melted_data)

   ID    Name Age     variable value
1   1   Alice  25 Group1_Var1     1
2   2     Bob  30 Group1_Var1     2
3   3 Charlie  35 Group1_Var1     3
4   4   David  40 Group1_Var1     4
5   5     Eve  45 Group1_Var1     5
6   1   Alice  25 Group1_Var2     6
7   2     Bob  30 Group1_Var2     7
8   3 Charlie  35 Group1_Var2     8
9   4   David  40 Group1_Var2     9
10  5     Eve  45 Group1_Var2    10
11  1   Alice  25 Group2_Var1    11
12  2     Bob  30 Group2_Var1    12
13  3 Charlie  35 Group2_Var1    13
14  4   David  40 Group2_Var1    14
15  5     Eve  45 Group2_Var1    15
16  1   Alice  25 Group2_Var2    16
17  2     Bob  30 Group2_Var2    17
18  3 Charlie  35 Group2_Var2    18
19  4   David  40 Group2_Var2    19
20  5     Eve  45 Group2_Var2    20