How to get data for rows that follow certain pattern-CodePudding

I have a data frame that looks something like this:

x	y	z
23	1	1
23	4	2
23	56	1
23	59	2
15	89	1
15	12	1
15	15	2
17	18	1
17	21	2
78	11	1
78	38	1
78	41	2

Now this data has certain pattern on column y and column z. I want to get all the data where in column z we have a row wise pair of 2 followed by 1 for a given value in x. Simply put, we need to remove all rows that have 1 in column z but that 1 is not followed by 2 in next row.

The final output should look like this:

x	y	z
23	1	1
23	4	2
23	56	1
23	59	2
15	12	1
15	15	2
17	18	1
17	21	2
78	38	1
78	41	2

CodePudding user response：

library(tidyverse)

df <- data.frame(x = c(23,23,23,23,15,15,15,17,17,78,78,78),
                 y = c(1,4,56,59,89,12,15,18,21,11,38,41),
                 z = c(1,2,1,2,1,1,2,1,2,1,1,2))

df %>%
   filter(!(z == 1 & lead(z) != 2))

CodePudding user response：

You can do this:

library(dplyr)

df %>%
  group_by(x) %>%
  filter((((z == 1) & (lead(z) == 2)) | ((z == 2) & (lag(z) == 1))))

# A tibble: 10 × 3
# Groups:   x [4]
       x     y     z
   <int> <int> <int>
 1    23     1     1
 2    23     4     2
 3    23    56     1
 4    23    59     2
 5    15    12     1
 6    15    15     2
 7    17    18     1
 8    17    21     2
 9    78    38     1
10    78    41     2