R数据表计数值类型按组

Question

DATA=data.frame(SUBJECT=c(1,1,1,2,2,2,3,3,4), TIME=c(1,2,3,1,2,3,1,2,1),
TYPE=c("dog","dog","cat","cat","dog","cat","cat","cat","dog"),
FIRST=c("dog","dog","dog","cat","cat","cat","cat","cat","dog"),
LAST=c("cat","cat","cat","cat","cat","cat","cat","cat","dog"),
DOG=c(2,2,2,1,1,1,0,0,1),
CAT=c(1,1,1,2,2,2,2,2,0))

我有'DATA'和' subject ';和";TYPE"one_answers"TIME"，我希望创建"FIRST"， "LAST"， "DOG"， "CAT">

"数据"按主题和时间排序。

我希望创建一个变量FIRST，它等于列'TYPE'中报告的第一个值

我希望创建一个变量LAST，它等于列'TYPE'中报告的LAST值

然后我希望创建变量DOG和CAT，它们等于有多少个"狗"one_answers";cat">

Answer 1

library(data.table)
DT <- as.data.table(DATA[,1:3])
# step 1, get the first/last
DT[, c("FIRST", "LAST") := .(first(TYPE), last(TYPE)), by = .(SUBJECT) ]
DT
#    SUBJECT  TIME   TYPE  FIRST   LAST
#      <num> <num> <char> <char> <char>
# 1:       1     1    dog    dog    cat
# 2:       1     2    dog    dog    cat
# 3:       1     3    cat    dog    cat
# 4:       2     1    cat    cat    cat
# 5:       2     2    dog    cat    cat
# 6:       2     3    cat    cat    cat
# 7:       3     1    cat    cat    cat
# 8:       3     2    cat    cat    cat
# 9:       4     1    dog    dog    dog
# step 2, bring in the counts
counts <- dcast(DT[, .(n = .N), by = .(SUBJECT, TYPE)], SUBJECT ~ TYPE, value.var = "n", fill = 0)
counts
#    SUBJECT   cat   dog
#      <num> <int> <int>
# 1:       1     1     2
# 2:       2     2     1
# 3:       3     2     0
# 4:       4     0     1
counts[DT, on = .(SUBJECT)]
#    SUBJECT   cat   dog  TIME   TYPE  FIRST   LAST
#      <num> <int> <int> <num> <char> <char> <char>
# 1:       1     1     2     1    dog    dog    cat
# 2:       1     1     2     2    dog    dog    cat
# 3:       1     1     2     3    cat    dog    cat
# 4:       2     2     1     1    cat    cat    cat
# 5:       2     2     1     2    dog    cat    cat
# 6:       2     2     1     3    cat    cat    cat
# 7:       3     2     0     1    cat    cat    cat
# 8:       3     2     0     2    cat    cat    cat
# 9:       4     0     1     1    dog    dog    dog