Combining Multiple Geometries

This lesson is called Combining Multiple Geometries, part of the Mapping with R course. This lesson is called Combining Multiple Geometries, part of the Mapping with R course.

Transcript

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View code shown in video

library(sf)
library(tidyverse)
library(scales)

city_council_districts <-
  read_sf("https://raw.githubusercontent.com/rfortherestofus/mapping-with-r-v2/refs/heads/main/data/portland_city_council_districts.geojson")

city_council_districts |>
  mapview::mapview()

improved_corners_by_district <-
  read_sf("https://raw.githubusercontent.com/rfortherestofus/mapping-with-r-v2/refs/heads/main/data/improved_corners_by_district.geojson")

improved_corners_by_area <-
  improved_corners_by_district |>
  mutate(
    area = case_when(
      district == "District 4" ~ "Westside",
      .default = "Eastside"
    )
  ) |>
  group_by(area, ramp_style) |>
  summarize(n = sum(n)) |>
  ungroup() |>
  group_by(area) |>
  mutate(pct = n / sum(n)) |>
  ungroup()

improved_corners_by_area |>
  filter(ramp_style == "Improved") |>
  ggplot() +
  geom_sf(aes(fill = pct)) +
  labs(fill = NULL) +
  scale_fill_viridis_c(
    option = "B",
    limits = c(0.25, 0.35),
    labels = percent_format(accuracy = 1)
  ) +
  theme_void() +
  theme(
    legend.position = "top",
    legend.key.width = unit(2, "cm"),
    legend.key.height = unit(0.5, "cm")
  )

Your Turn

Combine all of the sextants to make a map that shows the Portland boundaries.

Learn More

In this lesson, I only covered using group_by() and summarize() to combine geometries and values within them. If you just need to combine geometries, you can also use the st_union() function.