是否在r中的数据帧的其他列中添加依赖于变量的索引?

cumsum a==-1

library(dplyr)

df1 %>%
  mutate(b = cumsum(a == -1) + 1)

df1$b = cumsum(df1$a == -1) + 1

# A tibble: 11 x 2
       a     b
   <dbl> <dbl>
 1     1     1
 2     1     1
 3    -1     2
 4     1     2
 5     1     2
 6     1     2
 7    -1     3
 8     1     3
 9     1     3
10     1     3
11     1     3

df1 = structure(list(a = c(1, 1, -1, 1, 1, 1, -1, 1, 1, 1, 1)), .Names = "a", row.names = c(NA, 
-11L), class = c("tbl_df", "tbl", "data.frame"))

1. 1 -1

2. index cumsum

   library(dplyr)
   
   df %>%
     mutate(helper = ifelse(row_number()==1, 1, 
       ifelse(a == -1, 1, 0))) %>% 
     mutate(index = cumsum(helper)) %>%
     select(-helper)