hourly sums with dplyr with zeros for empty hours - r

Question

I have a dataset similar to the format of "my_data" below, where each line is a single count of an event. I want to obtain a summary of how many events happen in every hour. I would like to have every hour with no events be included with a 0 for its "hourly_total" value.
I can achieve this with dplyr as shown, but the empty hours are dropped instead of being set to 0.
Thank you!
set.seed(123)
library(dplyr)
library(lubridate)
latemail <- function(N, st="2012/01/01", et="2012/1/31") {
st <- as.POSIXct(as.Date(st))
et <- as.POSIXct(as.Date(et))
dt <- as.numeric(difftime(et,st,unit="sec"))
ev <- sort(runif(N, 0, dt))
rt <- st + ev
}
my_data <- data_frame( fake_times = latemail(25),
count = 1)
my_data %>% group_by( rounded_hour = floor_date(fake_times, unit = "hour")) %>%
summarise( hourly_total = sum(count))

Answer 1

Assign your counts to an object
counts <- my_data %>% group_by( rounded_hour = floor_date(fake_times, unit = "hour")) %>%
summarise( hourly_total = sum(count))
Create a data frame with all the necessary hours
complete_data = data.frame(hour = seq(floor_date(min(my_data$fake_times), unit = "hour"),
floor_date(max(my_data$fake_times), unit = "hour"),
by = "hour"))
Join to it and fill in the NAs.
complete_data %>% group_by( rounded_hour = floor_date(hour, unit = "hour")) %>%
left_join(counts) %>%
mutate(hourly_total = ifelse(is.na(hourly_total), 0, hourly_total))