r - 在 R 中按顺序标记句子？

Question

我有一个单词列表，我想将它们组合成句子。数据目前采用以下格式:

df <- data_frame(word = c("I'm", "going", "to", "be", "sick", "I", "want", "to", "go", "home"),
             stop = c(FALSE, FALSE, FALSE, FALSE, TRUE, FALSE, FALSE, FALSE, FALSE, TRUE))

我想按顺序将每个停用词后面的每个句子标记到一个新列中，以便数据如下所示:

df2 <- data_frame(word = c("I'm", "going", "to", "be", "sick", "I", "want", "to", "go", "home"),
             stop = c(FALSE, FALSE, FALSE, FALSE, TRUE, FALSE, FALSE, FALSE, FALSE, TRUE),
             num = c(1, 1, 1, 1, 1, 2, 2, 2, 2, 2))

有什么快速的方法可以做到这一点吗？谢谢!

Answer 1

library(tidyverse)
   df %>% mutate(num = cumsum(lag(stop, default = FALSE))+1)
    # A tibble: 10 x 3
       word  stop    num
       <chr> <lgl> <dbl>
     1 I'm   FALSE    1.
     2 going FALSE    1.
     3 to    FALSE    1.
     4 be    FALSE    1.
     5 sick  TRUE     1.
     6 I     FALSE    2.
     7 want  FALSE    2.
     8 to    FALSE    2.
     9 go    FALSE    2.
    10 home  TRUE     2.