Introduction to spatial data

Visualizing Geospatial Data in R

Charlotte Wickham

Assistant Professor at Oregon State University

What is spatial data?

Data is associated with locations
Location described by coordinates + a coordinate reference system (CRS)
Common CRS: longitude, latitude describes locations on the surface of the Earth

House sales in Corvallis

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House sales in Corvallis

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House sales in Corvallis

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House sales in Corvallis

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House sales in Corvallis

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House sales in Corvallis

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House sales in a data frame

head(sales)

        lon      lat  price bedrooms baths     
1 -123.2803 44.57808 267500        5     2     
2 -123.2330 44.59718 255000        3     2     
3 -123.2635 44.56923 295000        3     2
4 -123.2599 44.59453   5000        0     1     
5 -123.2632 44.53606  13950        0     2     
6 -123.2847 44.59877 233000        3     2

nrow(sales)

Point data: locations are points, described by a single pair of coordinates

Displaying spatial data with ggplot2

library(ggplot2)


ggplot(sales, aes(lon, lat)) + 
  geom_point()

Adding some location cues would be helpful

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The ggmap package

library(ggmap)


# Coordinates for location of interest
nyc <- c(lon = -74.0059, lat = 40.7128)


# 1. Download the relevant map
nyc_map <- get_map(location = nyc,
                   zoom = 10)


# 2. Display the map
ggmap(nyc_map)

NYC map

Let's practice!

Visualizing Geospatial Data in R