#30DayMapChallenge 2021 - Day 27 - Heatmap

heatmap.R

# Create a (not very good) heatmap of earthquakes in New Zealand
# For #30DayMapChallenge 2021 - Day 27 - Heatmap
#  -- David Friggens, November 2021


# Setup -------------------------------------------------------------------

library(readr)
library(dplyr)
library(sf)
library(rnaturalearth)
library(ggplot2)
library(ggmap)


# Data --------------------------------------------------------------------

# from https://quakesearch.geonet.org.nz
eq <-
  read_csv("data/earthquakes.csv") %>% 
  filter(eventtype == "earthquake") %>% 
  select(longitude, latitude, magnitude)
geo_eq <- 
  eq %>% 
  st_as_sf(coords = c("longitude", "latitude"), crs = 4326L)
eq_d1 <- 
  eq %>% 
  mutate(longitude = round(longitude, 1),
         latitude = round(latitude, 1)) %>% 
  group_by(longitude, latitude) %>% 
  summarise(magnitude = sum(magnitude)) %>% 
  ungroup()

nz <- 
  ne_countries(scale = "small", returnclass = "sf") %>%
  filter(iso_a3 == "NZL")


# Plot --------------------------------------------------------------------

gg_eq <- 
  ggmap(get_stamenmap(bbox = c(164, -48, 181.3, -33.8),
                    zoom = 6,
                    maptype = "watercolor")) +
  stat_density_2d(data = eq,
                  aes(x = longitude, y = latitude,
                      fill = ..level..),
                  geom = "polygon",
                  alpha = 0.3, colour = NA) +
  scale_fill_viridis_c() +
  theme_void() +
  theme(legend.position = "none")

ggsave(plot = gg_eq,
       "Day_27/Day_27_wc_eq.png",
       width = 20, height = 20, dpi = 72)