day_prob <-
  list(
    A = c(0.06, 0.06, pmax(dchisq(1:13, 3)*1, 0.06))
    , B = c(0.06, 0.06, pmax(dchisq(seq(1, 25, 2), 5)*6, 0.06))
  )

day_prob %>%
  lapply(function(x){
    tibble(
      Day = 1:length(x)
      , Prob = x
    )
  }) %>%
  bind_rows(.id = "Group") %>%
  ggplot(aes(x = Day
             , y = Prob
             , col = Group)) +
  geom_line() +
  geom_point() +
  scale_color_brewer(palette = "Dark2")

make_obs <- function(group, day){
  sapply(1:length(group), function(idx){
    rbinom(1, 1, day_prob[[group[idx]]][day[idx]] )
  })
}

set.seed(12345)
example_data <-
  tibble(
    Group = rep(c("A", "B"), each = 50)
    , Ind = 1:100
    , Day = 1
  ) %>%
  complete(nesting(Group, Ind), Day = 1:15) %>%
  mutate(
    Obs = make_obs(Group, Day)
  )

example_data %>%
  group_by(Group, Day) %>%
  summarise(Prop_pos = mean(Obs)) %>%
  ungroup() %>%
  ggplot(aes(x = Day
             , y = Prop_pos
             , col = Group)) +
  geom_line() +
  scale_color_brewer(palette = "Dark2")