Summarise hourly data by date

summarise_daily.R

library(dplyr)

## Make some mock data for illustration:
date_time <- seq(as.POSIXct("2014-01-01"), as.POSIXct("2015-08-18"), by = "1 hour")
value <- rnorm(length(date_time))
my_data <- data.frame(date_time, value)

# Create a date column (remove time)
my_data$date <- as.Date(my_data$date_time, tz = "Canada/Pacific")

# Group by date and summarise values
my_data_summarized <- group_by(my_data, date) %>% 
  summarise(daily_mean = mean(value))