R DataTable解快速整形

Question

    data1=data.frame("StudentID"=c(1,2,3,4,5),
                    "a1cat"=c(9,10,2,0,10),
                    "a2cat"=c(0,2,8,6,7),
                    "a3cat"=c(4,2,1,6,5),
                    "a1dog"=c(8,4,4,5,8),
                    "a2dog"=c(1,9,10,5,7),
                    "a3dog"=c(9,3,2,7,7),
                    "q20fox"=c(2,8,6,1,9),
"q22fox"=c(8,10,9,6,6),
                        "q24fox"=c(5,0,2,9,7))


        data2=data.frame("StudentID" = sort(rep(1:5,each=3)),
    "timeX" = c(1,2,3,1,2,3,1,2,3,1,2,3,1,2,3),
                         "meow" = c(9,0,4,10,2,2,2,8,1,0,6,6,10,7,5),
                         "bark" = c(8,1,9,4,9,3,4,10,2,5,5,7,8,7,7),
                         "woof"=c(2,8,5,8,10,0,6,9,2,1,6,9,9,6,7))

我有'data1‘，并希望得到'data2’使用data.table重塑数据，并给出每一列的新名称。

    data1x=data.frame("StudentID"=c(1,2,3,4,5),
                    "a1cat"=c(9,10,2,0,10),
                    "a2cat"=c(0,2,8,6,7),
                    "a3cat"=c(4,2,1,6,5),
                    "a1dog"=c(8,4,4,5,8),
                    "a2dog"=c(1,9,10,5,7),
                    "a3dog"=c(9,3,2,7,7),
                    "fox20"=c(2,8,6,1,9),
"fox22"=c(8,10,9,6,6),
                        "fox24"=c(5,0,2,9,7))

Answer 1

我们可以将melt与measure patterns结合使用

library(data.table)
melt(setDT(data1), measure = patterns("cat$", "dog$", "fox\\d*$"), 
     value.name = c("meow", "bark", "woof"), 
         variable.name = 'timeX')[order(StudentID)]
#     StudentID timeX meow bark woof
# 1:         1     1    9    8    2
# 2:         1     2    0    1    8
# 3:         1     3    4    9    5
# 4:         2     1   10    4    8
# 5:         2     2    2    9   10
# 6:         2     3    2    3    0
# 7:         3     1    2    4    6
# 8:         3     2    8   10    9
# 9:         3     3    1    2    2
#10:         4     1    0    5    1
#11:         4     2    6    5    6
#12:         4     3    6    7    9
#13:         5     1   10    8    9
#14:         5     2    7    7    6
#15:         5     3    5    7    7