Calculates state level Cook PVI using their current weighting.

cook_pvi.R

library(tidyverse)

## Data from: https://dataverse.harvard.edu/dataset.xhtml?persistentId=doi%3A10.7910%2FDVN%2F42MVDX
df <- read_csv("1976-2020-president.csv")

cook_pvi <- df |> filter(party_simplified%in% c("DEMOCRAT", "REPUBLICAN")) |> 
  select(year, state, party_simplified, candidatevotes) |> 
  pivot_wider(id_cols=c(year,state), 
              names_from = party_simplified, 
              values_from=candidatevotes, values_fn=sum) |> 
  mutate(percent = DEMOCRAT/(DEMOCRAT+REPUBLICAN)*100) |> 
  group_by(year) |> 
  mutate(national_percentage = sum(DEMOCRAT)/sum(DEMOCRAT+REPUBLICAN)*100) |> 
  mutate(lean = percent-national_percentage) |> 
  select(year, state, lean) |> 
  group_by(state) |> 
  mutate(pvi = (lean*3/4 + lag(lean)/4)) |> 
  complete(year=full_seq(year, 2)) |> 
  fill(pvi, .direction="down") |> 
  mutate(year=year + 2)