Use the development version of ggplot2 to get access to geom_sf().

# devtools::install_github("tidyverse/ggplot2")
library(openintro)
## Please visit openintro.org for free statistics materials
## 
## Attaching package: 'openintro'
## The following objects are masked from 'package:datasets':
## 
##     cars, trees
library(tidycensus)
## Warning: package 'tidycensus' was built under R version 3.4.2
library(tidyverse)
## Loading tidyverse: ggplot2
## Loading tidyverse: tibble
## Loading tidyverse: tidyr
## Loading tidyverse: readr
## Loading tidyverse: purrr
## Loading tidyverse: dplyr
## Warning: package 'dplyr' was built under R version 3.4.2
## Conflicts with tidy packages ----------------------------------------------
## filter(): dplyr, stats
## lag():    dplyr, stats
library(viridis)
## Loading required package: viridisLite
library(stringr)
census_api_key("7491cf955005ef7221778ebe1228115c53a12df6")
## To install your API key for use in future sessions, run this function with `install = TRUE`.
centroids <- read_delim("~/Dropbox/Documents/SMU/CSC 463/Fall 2017 Main/centroids.txt", 
"\t", escape_double = FALSE, col_types = cols(GEOID = col_character()),trim_ws = TRUE)

Let’s look at median household income in the last 12 months for the State of Washington using ACS 2015 5 year estimates.

options(tigris_use_cache = TRUE)

medhh <- get_acs(state = "WA", geography = "county", 
                  variables = "B19013_001", geometry = TRUE)

head(medhh)
## Simple feature collection with 6 features and 5 fields
## geometry type:  MULTIPOLYGON
## dimension:      XY
## bbox:           xmin: -124.7631 ymin: 45.83596 xmax: -117.8194 ymax: 48.55072
## epsg (SRID):    4269
## proj4string:    +proj=longlat +datum=NAD83 +no_defs
## # A tibble: 6 x 6
##   GEOID                        NAME   variable estimate   moe
##   <chr>                       <chr>      <chr>    <dbl> <dbl>
## 1 53005   Benton County, Washington B19013_001    60251  1370
## 2 53007   Chelan County, Washington B19013_001    51837  1886
## 3 53009  Clallam County, Washington B19013_001    47253  1606
## 4 53015  Cowlitz County, Washington B19013_001    47452  1861
## 5 53037 Kittitas County, Washington B19013_001    46458  3093
## 6 53043  Lincoln County, Washington B19013_001    46069  1791
## # ... with 1 more variables: geometry <S3: sfc_MULTIPOLYGON>
medhh %>%
  mutate(NAME = str_replace(NAME,'County, Washington','')) %>% 
  ggplot(aes(x = estimate, y = reorder(NAME, estimate))) + 
  geom_point()

medhh %>% 
  ggplot(aes(fill = estimate, color = estimate)) + 
  geom_sf() + 
  coord_sf(crs = 26911) + 
  scale_fill_viridis(option = "magma") + 
  scale_color_viridis(option = "magma")

cc = countyComplete %>% 
  filter(state == "Washington") %>% 
  select(FIPS,pop2010) %>%
  rename(GEOID = FIPS) %>% 
  mutate(GEOID = as.character(GEOID))
  
select(centroids,GEOID,LAT,LONG) %>%
  full_join(cc) %>% 
  full_join(medhh) -> medhhc
## Joining, by = "GEOID"
## Joining, by = "GEOID"
 medhhc  %>%  ggplot(aes(x=LONG,y=LAT)) +
  geom_sf() +
  geom_point(aes(color=estimate,size=pop2010)) +
  scale_color_viridis(option = "magma")