R code to create a plot of parishes by party holding the corresponding Westminster seat

parish_control.R

library(tidyverse)
library(rio)
library(hrbrthemes)

### (1) Get files in
### Parish to Ward
### https://geoportal.statistics.gov.uk/datasets/ons::parish-to-ward-to-local-authority-district-december-2020-lookup-in-england-and-wales-v2/about

par2ward <- read.csv("Parish_to_Ward_to_Local_Authority_District__December_2020__Lookup_in_England_and_Wales_V2.csv")
par2ward$FID <- NULL

### Ward to Westminster
### https://geoportal.statistics.gov.uk/datasets/063ccaa43b9a4f4281b3ad803c1ed2e8_0/explore
ward2pcon <- read.csv("Ward_to_Westminster_Parliamentary_Constituency_to_Local_Authority_District_to_Upper_Tier_Local_Authority__December_2020__Lookup_in_the_United_Kingdom_V2.csv")
ward2pcon$FID <- NULL

### General election results
### https://www.britishelectionstudy.com/data-objects/linked-data/
ge19 <- rio::import("BES-2019-General-Election-results-file-v1.1.xlsx")

### (2) Start merging
### Create parish to constituency
par2con <- merge(par2ward, ward2pcon,
                 by = c("WD20CD", "WD20NM"),
                 all.x = TRUE,
                 all.y = FALSE)

### Add on party holding constituency
par2con <- merge(par2con,
                 ge19,
                 by.x = "PCON20CD",
                 by.y = "ONSConstID")


### Sometimes this gives up multiple parishes because one parish straddles two wards
### Resolve this

par2con <- par2con %>%
    group_by(PAR20CD, PAR20NM) %>%
    summarize(nDistinct = length(unique(PCON20CD)),
              nParties = length(unique(Winner19)),
              isCon = all(Winner19 == "Conservative"),
              party = case_when(nParties > 1 ~ "Mixed",
                                nParties == 1 ~ unique(Winner19)))

table(par2con$nParties)

plot.df <- par2con %>%
    group_by(party) %>%
    tally()

p1 <- ggplot(plot.df, aes(x = party, y = n, fill = party)) +
    geom_col() +
    scale_x_discrete("Party") +
    scale_y_continuous("Number of parishes") +
    labs(title = "Number of parishes according to\n party holding the corresponding Westminster constituency") +
    scale_fill_manual(values = c("#0087DC",
                                 "#E4003B",
                                 "#FAA61A",
                                 "#CCCCCC",
                                 "#005B54",
                                 "#CCCCCC"),
                      guide = "none") +
    coord_flip() + 
    theme_ipsum()

ggsave(p1, file = "parish_control.png", width = 12, height = 7)