Question

数据框包含三个变量：ID，状态（因子）和t（整数）。每个ID可能有多个观察结果。见下文

id <- c(1,1,1,1,1,2,2,2,2,3,4,4,4,5,5)
state <- c("a", "b", "c", "d", "e", "a", "a", "c", "e", "b", "e", "a", "c", "b", "a")
t <- c(1,2,3,4,5, 1,2,3,4, 1, 1,2,3, 1,2)

dat <- data.frame(id, state, t)

我想创建一个包含两个变量的新数据框：＆＃34;来自＆＃34;和＆＃34;到＆＃34;。对于每个ID，我想看看状态如何变化：例如，对于ID，状态从a移动到b，然后b移到c，然后c移到d，最后移到d到e。如果有任何ID的记录，那么忽略（例如，ID = 3）。

# The final data set looks like:
from <- c("a", "b", "c", "d", "a", "a", "c", "e", "a", "b")
to <- c("b", "c", "d", "e", "a", "c", "e", "a", "c", "a")

dat2 <- data.frame(from, to)

Answer 1

我们可以尝试使用data.table。转换＆＃39; data.frame＆＃39;到＆＃39; data.table＆＃39; （setDT(dat)），按＆＃39; id＆＃39;分组，删除状态＆＃39;中的最后一个观察值。从＆＃39;创建＆＃39;并首先观察创建＆＃39;到＆＃39;

library(data.table)
setDT(dat)[, .(from = state[-.N], to = state[-1]), id][, id := NULL][]
#     from to
# 1:    a  b
# 2:    b  c
# 3:    c  d
# 4:    d  e
# 5:    a  a
# 6:    a  c
# 7:    c  e
# 8:    e  a
# 9:    a  c
#10:    b  a

使用＆＃34;从＆＃34;重新整形R中的数据和＆＃34;到＆＃34;

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