Practice drawing vector maps
library(tidyverse)
library(sf)
library(tidycensus)
library(viridis)
# useful on MacOS to speed up rendering of geom_sf() objects
if (!identical(getOption("bitmapType"), "cairo") && isTRUE(capabilities()[["cairo"]])) {
options(bitmapType = "cairo")
}
options(digits = 3)
set.seed(1234)
theme_set(theme_minimal())
American Community Survey
The U.S. Census Bureau conducts the American Community Survey which gathers detailed information on topics such as demographics, employment, educational attainment, etc. They make a vast portion of their data available through an application programming interface (API), which can be accessed intuitively through R via the tidycensus package. We previously discussed how to use this package to obtain statistical data from the decennial census. However the Census Bureau also has detailed information on political and geographic boundaries which we can combine with their statistical measures to easily construct geospatial visualizations.
If you have not already, obtain an API key and store it securely on your computer.
Exercise: Visualize income data
Obtain information on median household income in 2017 for Cook County, IL at the tract-level using the ACS. To retrieve the geographic features for each tract, set
geometry = TRUEin your function.You can use `load_variables(year = 2017, dataset = "acs5")` to retrieve the list of variables available and search to find the correct variable name.Click for the solution
cook_inc <- get_acs( state = "IL", county = "Cook", geography = "tract", variables = c(medincome = "B19013_001"), year = 2017, geometry = TRUE )cook_inc## Simple feature collection with 1319 features and 5 fields (with 1 geometry empty) ## Geometry type: MULTIPOLYGON ## Dimension: XY ## Bounding box: xmin: -88.3 ymin: 41.5 xmax: -87.5 ymax: 42.2 ## Geodetic CRS: NAD83 ## First 10 features: ## GEOID NAME variable estimate ## 1 17031010201 Census Tract 102.01, Cook County, Illinois medincome 40841 ## 2 17031030200 Census Tract 302, Cook County, Illinois medincome 64089 ## 3 17031031700 Census Tract 317, Cook County, Illinois medincome 44555 ## 4 17031031900 Census Tract 319, Cook County, Illinois medincome 61211 ## 5 17031050200 Census Tract 502, Cook County, Illinois medincome 74375 ## 6 17031051300 Census Tract 513, Cook County, Illinois medincome 149271 ## 7 17031061500 Census Tract 615, Cook County, Illinois medincome 117656 ## 8 17031062600 Census Tract 626, Cook County, Illinois medincome 144211 ## 9 17031063400 Census Tract 634, Cook County, Illinois medincome 95488 ## 10 17031070600 Census Tract 706, Cook County, Illinois medincome 151250 ## moe geometry ## 1 7069 MULTIPOLYGON (((-87.7 42, -... ## 2 12931 MULTIPOLYGON (((-87.7 42, -... ## 3 12220 MULTIPOLYGON (((-87.7 42, -... ## 4 6343 MULTIPOLYGON (((-87.7 42, -... ## 5 18773 MULTIPOLYGON (((-87.7 42, -... ## 6 26389 MULTIPOLYGON (((-87.7 41.9,... ## 7 11416 MULTIPOLYGON (((-87.7 41.9,... ## 8 22537 MULTIPOLYGON (((-87.7 41.9,... ## 9 4904 MULTIPOLYGON (((-87.6 41.9,... ## 10 47800 MULTIPOLYGON (((-87.7 41.9,...Draw a choropleth using the median household income data. Use a continuous color gradient to identify each tract’s median household income.
Click for the solution
ggplot(data = cook_inc) + # use fill and color to avoid gray boundary lines geom_sf(aes(fill = estimate, color = estimate)) + # increase interpretability of graph scale_color_continuous(labels = scales::dollar) + scale_fill_continuous(labels = scales::dollar) + labs( title = "Median household income in Cook County, IL", subtitle = "In 2017", color = NULL, fill = NULL, caption = "Source: American Community Survey" )
Exercise: Customize your maps
Draw the same choropleth for Cook County, but convert median household income into a discrete variable with 6 levels.
Click for the solution
* Using `cut_interval()`:cook_inc %>% mutate(inc_cut = cut_interval(estimate, n = 6)) %>% ggplot() + # use fill and color to avoid gray boundary lines geom_sf(aes(fill = inc_cut, color = inc_cut)) + # increase interpretability of graph labs( title = "Median household income in Cook County, IL", subtitle = "In 2017", color = NULL, fill = NULL, caption = "Source: American Community Survey" )
* Using `cut_number()`:cook_inc %>% mutate(inc_cut = cut_number(estimate, n = 6)) %>% ggplot() + # use fill and color to avoid gray boundary lines geom_sf(aes(fill = inc_cut, color = inc_cut)) + # increase interpretability of graph labs( title = "Median household income in Cook County, IL", subtitle = "In 2017", color = NULL, fill = NULL, caption = "Source: American Community Survey" )
Draw the same choropleth for Cook County using the discrete variable, but select an appropriate color palette using Color Brewer.
Click for the solution
* Using `cut_interval()` and the Blue-Green palette:cook_inc %>% mutate(inc_cut = cut_interval(estimate, n = 6)) %>% ggplot() + # use fill and color to avoid gray boundary lines geom_sf(aes(fill = inc_cut, color = inc_cut)) + scale_fill_brewer(type = "seq", palette = "BuGn") + scale_color_brewer(type = "seq", palette = "BuGn") + # increase interpretability of graph labs( title = "Median household income in Cook County, IL", subtitle = "In 2017", color = NULL, fill = NULL, caption = "Source: American Community Survey" )
* Using `cut_number()` and the Blue-Green palette:cook_inc %>% mutate(inc_cut = cut_number(estimate, n = 6)) %>% ggplot() + # use fill and color to avoid gray boundary lines geom_sf(aes(fill = inc_cut, color = inc_cut)) + scale_fill_brewer(type = "seq", palette = "BuGn") + scale_color_brewer(type = "seq", palette = "BuGn") + # increase interpretability of graph labs( title = "Median household income in Cook County, IL", subtitle = "In 2017", color = NULL, fill = NULL, caption = "Source: American Community Survey" )
You can choose any palette that is for sequential data.Use the
viridiscolor palette for the Cook County map drawn using the continuous measure.Click for the solution
ggplot(data = cook_inc) + # use fill and color to avoid gray boundary lines geom_sf(aes(fill = estimate, color = estimate)) + # increase interpretability of graph scale_color_viridis(labels = scales::dollar) + scale_fill_viridis(labels = scales::dollar) + labs( title = "Median household income in Cook County, IL", subtitle = "In 2017", color = NULL, fill = NULL, caption = "Source: American Community Survey" )
Session Info
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