В качестве альтернативы, здесь есть tidyverse
способ
df %>%
mutate_if(is.factor, as.character) %>%
mutate(is_weekday = 1 - as.numeric(str_detect("Saturday|Sunday", days)))
# UID days is_weekday
#1 152 Monday 1
#2 145 Tuesday 1
#3 162 Thursday 1
#4 234 Sunday 0
Пример данных
df <- read.table(text =
"UID days
152 Monday
145 Tuesday
162 Thursday
234 Sunday", header = T)