Two-in-a-row below a threshold

two-in-a-row-example.R

# x is assumed to be a numeric vector
# output will be TRUE if both that value and the previous value are strictly below the threshold, FALSE otherwise
f <- function(x, threshold) {
  less_than <- (x < threshold)
  
  less_than & c(FALSE, !diff(less_than))
}


#### usage ####

x <- c(9,8,7,6,8,9,4,3,3,9)
f(x, 8)

library(dplyr)

tbl <- tibble(id = LETTERS[1:10], val = x)
tbl

tbl %>% mutate(two_in_a_row = f(x, 8))