## ----setup, include = FALSE---------------------------------------------------
knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>"
)

## -----------------------------------------------------------------------------
# check version number
process <- as.numeric(version$major) + as.numeric(version$minor)/10 > 4.2

## -----------------------------------------------------------------------------
# load the library
library(skylight)

# calculate sky illuminance values for
# a single date/time and location
df <- skylight(
      longitude = -135.8,
      latitude = -23.4,
      date = as.POSIXct("1986-12-18 21:00:00", tz = "GMT"),
      sky_condition = 1
    )

print(df)

## -----------------------------------------------------------------------------
# Generate a dataset with 15 minute values
# for approximately two months
input <- data.frame(
  longitude = 0,
  latitude = 50,
  date =  as.POSIXct("2020-06-18 00:00:00", tz = "GMT") + seq(0, 29*24*3600, 1800),
  sky_condition = 1
)

# calculate sky illuminance values for
# a single date/time and location
df <- skylight(
      longitude = input$longitude,
      latitude = input$latitude,
      date = input$date,
      sky_condition = 1
    )

print(head(df))

# previous results are of the same dimension (rows)
# as the input data and can be bound together
# for easy plotting
input <- cbind(input, df)

## -----------------------------------------------------------------------------
library(ggplot2)

ggplot(input) +
  geom_tile(
    aes(
      as.Date(date),
      as.numeric(format(date, "%H")) + as.numeric(format(date, "%M"))/60,
      fill = log(total_illuminance)
    )
  ) +
  scale_fill_viridis_c(
    option = "B"
  ) +
  labs(
    title = "Diurnal cycles of total illuminance",
    subtitle = "(including the effect of moon contributions)",
    y = "Hour",
    x = ""
  ) +
  theme(
    legend.position = "bottom"
  )

## ----echo = FALSE, warning=FALSE, message=FALSE, eval = process---------------
library(dplyr)
library(tidyr)

df <- input |>
  filter(
    moon_fraction == 100
  ) |>
  mutate(
    hour = as.numeric(format(date, "%H")),
    hour = ifelse(hour >= 12, hour - 24, hour)
  ) |>
  group_by(hour) |>
  summarize(
    sun_illuminance = mean(sun_illuminance),
    moon_illuminance = mean(moon_illuminance),
    total_illuminance = mean(total_illuminance),
    .groups = "drop"
  ) |>
  tidyr::pivot_longer(
    cols = ends_with("illuminance"),
    names_to = "illuminance"
  )

p <- ggplot(df) +
  geom_path(
    aes(
      hour,
      log(value),
      group = illuminance,
      colour = illuminance
    )
  ) +
  coord_cartesian(
    ylim = c(-4, 2),
    xlim = c(-5, 5)
  ) +
  labs(
    title = "Components of total illuminance",
    subtitle = "(30min increments during full moon)",
    x = "Hour (centered on midnight)"
  )

print(p)

## ----eval = process-----------------------------------------------------------
# recreating the data frame with parameters
# as before
input <- data.frame(
  longitude = 0,
  latitude = 50,
  date =  as.POSIXct("2020-06-18 00:00:00", tz = "GMT") + seq(0, 1*24*3600, 1800),
  sky_condition = 1
)

# but now using the piped approach to calculate
# all values

df <- input |> skylight()

print(head(df))