索引 R 数据框中两个特定字符值之间的所有行

Question

I have created a data frame z.

a = c(1,1,1)
b = c("start",2,2)
c = c(3,3,3)
d = c("end",4,4)

z = data.frame(rbind(a,b,c,d))
z

How can I index to get the row numbers between "start" and "end" if I don't know how many rows are going to be between "start" and "end"? In this instance there is only one row between "start" and "end" but for the next dataset there may be 50 rows between "start" and "end". Is there a way to use "start" and "end" to extract all the rows between them?

Answer 1

• We can use

library(dplyr)

z |> slice((which(X1 == "start")+1 ): (which(X1 == "end")-1))

• Or we can use grepl

z |> slice((which(grepl("start" , X1))+1):
           (which(grepl("end" , X1))-1))

Answer 2

You could do:

seq(which(z$X1 == 'start') + 1, which(z$X1 == 'end') - 1)
#> [1] 3