Find max of row cumulative sum of adjacent columns by group in R

I have this data frame. What I want to find is the maximum of row cumulative sums for each group given that they are adjacent and have values =1. For example, Group 1 has Year 1,2,3,4 adjacent and values add up =4, and year6 =1 so the max value is 4 for group 1 and so on. Below is an example of data frame and the desired result. Thank you

df <- data.frame(group = c(1:6),
             Year1 = c('1','0','0','0','0','0'),
             Year2 = c('1','1','1','0','1','1'),
             Year3 = c('1','1','0','0','1','0'),
             Year4 = c('1','1','1','0','1','1'),
             Year5 = c('0','0','1','1','1','1'),
             Year6 = c('1','0','0','0','0','1'))

df
      group Year1 Year2 Year3 Year4 Year5 Year6
1     1     1     1     1     1     0     1
2     2     0     1     1     1     0     0
3     3     0     1     0     1     1     0
4     4     0     0     0     0     1     0
5     5     0     1     1     1     1     0
6     6     0     1     0     1     1     1
result <- data.frame(group=c(1:6), value = c(4, 3, 2, 1, 4, 3))

result
  group value
1     1     4
2     2     3
3     3     2
4     4     1
5     5     4
6     6     3

>Solution :

We can write a function that will return the maximum of row cumulative sums for each group.

get_max_length <- function(x) {
  rl <- rle(x)
  max(rl$lengths[rl$values == 1])
}

Now we can apply this function for each row.

In base R, using apply

cbind(df[1], value = apply(df[-1], 1, get_max_length))

#  group value
#1     1     4
#2     2     3
#3     3     2
#4     4     1
#5     5     4
#6     6     3

Or with dplyr rowwise :

library(dplyr)

df %>%
  rowwise() %>%
  transmute(group, 
            value = get_max_length(c_across(starts_with("Year")))) %>%
  ungroup()