Boston precinct results for Question 2

# read shapefile of boston precincts
boston <- fortify(
    readOGR(dsn='WDPC_2015', layer='WDPC_2015'), region='WARD_PRECI')

## OGR data source with driver: ESRI Shapefile 
## Source: "WDPC_2015", layer: "WDPC_2015"
## with 255 features
## It has 7 fields

# read csv of boston precinct election results,
# rename precinct to id,
# create a new column: no percent - yes percent,
# and only look at precincts with more than one vote
results <- read.csv('./boston-question-2.csv') %>%
    rename(id = precinct) %>%
    filter(total.votes > 1) %>%
    mutate(pct = ifelse(yes.pct > 50, yes.pct, -no.pct))

# create intervals
results.intervals <- classIntervals(results$pct, style = 'fixed',
    fixedBreaks = c(-80, -75, -70, -65, -60, -55, -50, 50, 55, 60, 65, 70))$brks

# bin data into intervals
results$breaks <- cut(results$pct, breaks=results.intervals, include.lowest = TRUE)

# join shapefile with results
data <- left_join(boston, results)

# create color ramp
colors <- c(
    '#393d41',
    '#733236',
    '#aa2b31',
    '#db6950',
    '#f79659',
    '#ffce7a',
    '#d9e2cc',
    '#b7c28c',
    '#9dae77',
    '#66724d'
)

# make plot
ggplot() +
    geom_polygon(data=data, aes(x=long, y=lat, group=group, fill=breaks)) +
    ggtitle('Margin of victory for ballot question 2') +
    coord_map() +
    scale_fill_manual(values=colors) +
    theme_void()