This exercise will show you how to use ggmap to produce maps and combine them with data and the ggplot2 skills you have learned for geospatial visualisation.

1 Installing requirements

Lets start by installing and loading the required packages. Note that we are using the github version of ggmap. If you have already installed some of the packages you can skip those.

2 Maps | get_map() and ggmap()

As the name suggests, the get_map function from ggmap is used to get maps. The maps are of the class ggmap and you can get many different maptypes.

  • Use ggmap(), the function, to plot a ggmap object created by get_map and try out a few maptypes.

Note: Unless you have adjusted ggmap settings with a google API key the get_map seems to be a bit unreliable during testing. If the command fails, try again a few times. Save it to a variable so you don’t have to keep querying the map servers.

Trying out some other maptypes:

3 Add data to the map

Being able to output maps is great but, as with everything in life, it becomes more interesting when you can overlay it with data.

3.1 Points | geocode() and geom_point()

ggmap::geocode() is a nifty function that returns the latitude and longitude of a location. Use this to get the geocode of a place within the map that you created earlier in the exercise. Your favourite gym or restaurant for example?

In my example code, I show how to use tibble to get geocodes for several locations and bind them together to a data.frame.

When you have your locations dataset ready, use geom_point to add markers to your map for your locations. Feel free to use geom_text to also add labels for your locations. Notice that you can treat the ggmap function like ggplot.

3.2 Routes | trek() and geom_path()

trek is a function from ggmap that takes a start location and a stop location and gives a list of latitude and longitude coordinates connecting the two. You can give several different modes of transit, but why anyone would choose anything other than bicycling is beyond me.

Combining trek and ggplot2 geom_path we can plot a route between two places, as long as one exists. Regrettably it doesn’t seem like airplane transits are included yet. Read the help page for trek and try it out.

Note: Make sure your background map covers both start and stop position!

3.3 Pubs

What do they mean by pubs? Do they mean publications? Nope! We are going to plot actual pubs, bars, inns in the UK using a public dataset from https://www.getthedata.com/open-pubs.

Download the dataset pubs.rda from course materials.

Note: I have processed this data slightly, to see how unhide the following code box.

Use what you have learned so far to complete as many tasks as you have time for. There is some help code and example plots of the town “Oldham” below, but really try to do it yourself before you unhide it.

  1. Load pubs.rda into R.
  2. Subset the dataset to a city.
  3. Get a map of the city with ggmap.
  4. Plot the position of the pubs onto the map using geom_point.
  5. Create another plot where you plot the density lines of pubs using geom_density2d.
  • Optional: Feel free to select an appropriate maptype that isn’t so busy with text, I suggest the darker toner ones.
  1. Fill the density lines by overlaying with stat_density_2d as well. Use parametergeom = "polygon".
  • Tip: You can use scale_fill_gradient2 and scale_alpha to adjust colors and alpha.

Example code: Don’t unhide unless you’ve tried!

Task 4:

Task 5:

Task 6:

Task 6, tweaked:

4 Session Info

  • This document has been created in RStudio using R Markdown and related packages.
  • For R Markdown, see http://rmarkdown.rstudio.com
  • For details about the OS, packages and versions, see detailed information below:
## R version 3.5.0 (2018-04-23)
## Platform: x86_64-apple-darwin16.7.0 (64-bit)
## Running under: macOS High Sierra 10.13.4
## 
## Matrix products: default
## BLAS: /System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/libBLAS.dylib
## LAPACK: /System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/libLAPACK.dylib
## 
## locale:
## [1] en_US.UTF-8
## 
## attached base packages:
## [1] stats     graphics  grDevices utils     datasets  methods   base     
## 
## other attached packages:
##  [1] bindrcpp_0.2.2  ggmap_2.7.900   forcats_0.3.0   stringr_1.3.1  
##  [5] dplyr_0.7.5     purrr_0.2.5     readr_1.1.1     tidyr_0.8.1    
##  [9] tibble_1.4.2    ggplot2_2.2.1   tidyverse_1.2.1 captioner_2.2.3
## [13] bookdown_0.7    knitr_1.20     
## 
## loaded via a namespace (and not attached):
##  [1] tidyselect_0.2.4  xfun_0.1          reshape2_1.4.3   
##  [4] haven_1.1.1       lattice_0.20-35   colorspace_1.3-2 
##  [7] htmltools_0.3.6   yaml_2.1.19       rlang_0.2.1      
## [10] pillar_1.2.3      foreign_0.8-70    glue_1.2.0       
## [13] modelr_0.1.2      readxl_1.1.0      jpeg_0.1-8       
## [16] bindr_0.1.1       plyr_1.8.4        munsell_0.4.3    
## [19] gtable_0.2.0      cellranger_1.1.0  rvest_0.3.2      
## [22] RgoogleMaps_1.4.2 psych_1.8.4       evaluate_0.10.1  
## [25] labeling_0.3      Cairo_1.5-9       parallel_3.5.0   
## [28] broom_0.4.4       Rcpp_0.12.17      backports_1.1.2  
## [31] scales_0.5.0      jsonlite_1.5      mnormt_1.5-5     
## [34] rjson_0.2.19      png_0.1-7         hms_0.4.2        
## [37] digest_0.6.15     stringi_1.2.2     grid_3.5.0       
## [40] rprojroot_1.3-2   bitops_1.0-6      cli_1.0.0        
## [43] tools_3.5.0       magrittr_1.5      lazyeval_0.2.1   
## [46] crayon_1.3.4      pkgconfig_2.0.1   MASS_7.3-49      
## [49] xml2_1.2.0        lubridate_1.7.4   rstudioapi_0.7   
## [52] assertthat_0.2.0  rmarkdown_1.9     httr_1.3.1       
## [55] R6_2.2.2          nlme_3.1-137      compiler_3.5.0

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