Make a simple chart of property prices from MBIE/MfE urban development capacity data

analysis-mbie-mfe-data.R

# -----------------------------------------------------------------------------
# Setup
library(magrittr)
library(lubridate)
library(tidyverse)
library(ggplot2)
library(scales)
source("clean-ggplot-theme.R")
# -----------------------------------------------------------------------------


# -----------------------------------------------------------------------------
# MBIE/MfE Urban Development Capacity data

# Load property data
dat_au <- read_csv("AU.csv")
names(dat_au) <- tolower(names(dat_au))
dat_au %<>%
  mutate(date = yq(paste(year(date), quarter(date), sep = "-"))) %>%
  arrange(name, date)

# Load 2013 areas table
areas2013 <- read_csv("2013_Areas_Table.csv")

# Join region to sales data by AU code
dat_au %<>%
  left_join(areas2013 %>% 
              select(AU2013_code, REGC2013_label) %>% 
              distinct(), 
            by = c("code" = "AU2013_code"))

# Plot median_sp_real by quarter for all area units
chart_median_sp_real <- dat_au %>%
  ggplot() + 
  geom_line(aes(x = date, y = median_sp_real, group = code), 
            colour = rgb(0, 0, 0, 0.03)) + 
  xlab("") + 
  ylab("") + 
  scale_y_continuous(labels = comma, 
                     limits = c(0, 3000000), 
                     breaks = seq(0, 3000000, 500000)) + 
  clean_theme()
print(chart_median_sp_real)

# Plot median_sp_real by quarter, highlight Auckland area units
chart_median_sp_real_auckland_highlight <- dat_au %>%
  mutate(region_group = ifelse(REGC2013_label == "Auckland Region", "Auckland", "All other regions")) %>%
  ggplot() + 
  geom_line(aes(x = date, y = median_sp_real, group = code, colour = region_group)) + 
  xlab("") + 
  ylab("") + 
  ggtitle("Median real selling price for census area units (2017 dollars)") + 
  scale_y_continuous(labels = comma, 
                     limits = c(0, 3000000), 
                     breaks = seq(0, 3000000, 500000)) +
  scale_colour_manual(values = c("Auckland" = rgb(0, 0, 0, 0.1), 
                                 "All other regions" = rgb(0, 0, 0, 0.06)), 
                      guide = FALSE) + 
  facet_wrap("region_group", nrow = 2, ncol = 1) + 
  clean_theme(base_size = 22)
png("cau-median-prices.png", width = 1600, height = 1200)
print(chart_median_sp_real_auckland_highlight)
dev.off()
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