I have a string that I've converted into a character vector:
string <- c("A","A","A","C","G","G","C","C","T","T","T","T")
I'd like to be able to output a table that shows the indices of the consecutive letters in the order they appear. for example:
letter start end
A 1 3
C 4 4
G 5 6
C 7 8
T 9 12
I've tried looking into str_locate and some other str functions but haven't been able to figure it out. Any help appreciated!
I will using cumsum after rle
s=rle(string)
v=cumsum(rle(string)$lengths)
data.frame('var'=s$values,'start'=v+1-s$lengths,'end'=v)
var start end
1 A 1 3
2 C 4 4
3 G 5 6
4 C 7 8
5 T 9 12
We can use split by the run-length-id of 'string' into a list, get the range of values, and rbind the list elements
rl <- rle(string)
lst <- lapply(split(seq_along(string), rep(seq_along(rl$values), rl$lengths)), range)
names(lst) <- r1$values
do.call(rbind, lst)
# [,1] [,2]
#A 1 3
#C 4 4
#G 5 6
#C 7 8
#T 9 12
Or in a compact way
library(data.table)
data.table(letter = string)[, .(letter = letter[1], start = .I[1],
end = .I[.N]), rleid(letter)]
Or with tidyverse
library(tidyverse)
library(data.table)
string %>%
tibble(letter = .) %>%
mutate(rn = row_number()) %>%
group_by(grp = rleid(letter)) %>%
summarise(letter = first(letter),
start = first(rn),
end = last(rn)) %>%
ungroup %>%
select(-grp)
