Example for creating weekly index

week_index.R

df <- data.frame(date = seq.Date(from = as.Date("2020-01-01"), 
                                 length.out = 100, 
                                 by = "week")) %>%
  dplyr::mutate(week_index = 1 + (as.numeric(date) - as.numeric(min(date)))/7)


head(df)

# Creating data.frame with a date column
df <- data.frame(date = seq.Date(from = as.Date("2020-01-01"), 
                                 length.out = 100, 
                                 by = "week")) 

# Creating weekly index
df$week_index <- (as.numeric(df$date) - as.numeric(min(df$date))) / 7 + 1


head(df)