How to Scrape/Calculate State-by-state Population Per Electoral College Elector

population-per-elector.R

library(tidyverse)
library(rvest)
library(jsonlite)
library(xtable)

## How many Electoral College electors per state? ==============================
## Page as is for Sep 1, 2020
url_270 <- "https://www.270towin.com"
electors <- read_html(url_270) %>%
  html_nodes("script") %>%
  html_nodes(xpath = '//*[@type="text/javascript"]') %>%
  html_text() %>%
  .[grepl("https://www.270towin.com/maps/", .)] %>%
  ## string text surrounding the JSON structure
  ## regex after manual inspection
  ## Class, make sure to check the page source code to see what I am doing!
  str_match(., pattern = "races = (.*?);\n        map_d3") %>%
  .[[2]] %>%
  fromJSON(str_match(., pattern = "races = (.*?);\n        map_d3")[, 2]) %>%
  map(~ tibble(state = .x$state_name, electors = as.numeric(.x$e_votes))) %>%
  bind_rows()

## How does this compare against population? ===================================
pop_state <- paste0(
  ## Census estimate of state-by-state population
  "http://www2.census.gov/programs-surveys/popest/datasets/2010-2019/national/",
  "totals/nst-est2019-alldata.csv"
) %>%
  ## read_csv does not require that a file is in the hard drive
  read_csv() %>%
  select(state = NAME, pop = POPESTIMATE2019)

## Join then arrange by population per elector =================================
df <- left_join(electors, pop_state) %>%
  mutate(
    ## Convert population to million (scientific notation is 1e6)
    pop = pop / 1e6,
    pop_per_elector = pop / electors
  ) %>%
  arrange(desc(pop_per_elector))

## Were states matched perfectly by name? No? Good. ============================
any(is.na(df$pop_per_elector))

## Export to LaTeX =============================================================
print(
  ## No caption or labels
  xtable(
    ## Set column names
    df %>%
      rename(
        State = state,
        Electors = electors,
        `Pop. 2019 (million)` = pop,
        `Pop. Per Elector` = pop_per_elector
      ),
    digits = c(0, 0, 0, 2, 2)
  ),
  include.rownames = FALSE,
  booktabs = TRUE
)