Просто отрицайте значения:
M %>% mutate(quantile = ntile(-Score, 10))
Пример:
df1 %>%
mutate(quantile = ntile(-score, 3))
# # A tibble: 6 x 4
# ntile date score quantile
# <int> <date> <dbl> <int>
# 1 1 2005-08-31 -2.39 3
# 2 1 2005-09-30 0.573 2
# 3 1 2005-10-31 -1.61 3
# 4 1 2005-11-30 5.43 1
# 5 1 2005-12-31 0.106 2
# 6 1 2006-01-31 6.66 1
Данные игрушек:
df1 <- structure(list(ntile = c(1L, 1L, 1L, 1L, 1L, 1L),
date = structure(c(13026, 13056, 13087, 13117, 13148, 13179),
class = "Date"),
score = c(-2.38916419707325, 0.572675136581781, -1.61130358515631,
5.42706994951004, 0.105533424368025, 6.65697289481407)),
row.names = c(NA, -6L), class = c("tbl_df", "tbl", "data.frame"))