Graph the democratic margin on the generic ballot

democrats_generic_ballot.R

library(tidyverse)
polls_2018 <- read_tsv("http://elections.huffingtonpost.com/pollster/api/v2/questions/18-US-House/poll-responses-clean.tsv") %>% 
    filter(month(end_date)>=6) %>% 
    mutate(Dem.Margin = Democrat-Republican) %>%
    group_by(mode) %>%
    mutate(mean_dem = mean(Dem.Margin))
    
ggplot(polls_2018,aes(x=Dem.Margin,fill=Dem.Margin>0,col=Dem.Margin>0)) + 
    geom_bar(width=0.8,alpha=0.5) + 
    scale_color_manual(values=c("TRUE"="blue","FALSE"="red")) + 
    scale_fill_manual(values=c("TRUE"="blue","FALSE"="red")) + 
    facet_wrap(~mode) + 
    geom_vline(aes(xintercept=mean_dem)) + 
    geom_text(aes(x=mean_dem+1,y=15,label=sprintf("Mean: D+%s%%",round(mean_dem))),col='black',linetype=2,hjust=0) +
    labs(title="Different Polls Tell Different Stories of the 2018 House Midterms",
        subtitle="Depending on how you sample Americans, Democrats have a smaller or larger lead in the generic ballot",
        x="Democratic Margin (%)",
        y= "Number of Polls",caption="Source: Huffington Post Pollster")