---
title: "Exercises 1"
subtitle: "Medium level"
format: html
---

E1. Programmatically download borders of Germany (hint: you can try to use packages, such as {rgeoboundaries}, {geodata}, or {rnaturalearth}).

E2. Read the median (P50) global snow cover monthly values for December 2019 from  https://zenodo.org/record/6011200/ (hint2: you can create a connection to the file with the `/vsicurl/` prefix; see https://geocompr.robinlovelace.net/read-write.html#raster-data-read).

E3. Limit the snow cover data extent to the area of Germany (hint: see https://geocompr.robinlovelace.net/raster-vector.html#raster-cropping).

E4. Transform the Germany borders and the Germany snow cover data to a local projection (hint: try https://epsg.io/4839).

E5. Create a map of the median (P50) Germany snow cover monthly values for December 2019 using the {tmap} package. Customize map colors, add a scale bar, north arrow, graticule lines, and a map title (hint: look at the examples at https://r-tmap.github.io/tmap-book/nutshell.html#regular-maps).

E6. Save the map created in the previous exercise to a .png file (hint: look at the examples at https://r-tmap.github.io/tmap-book/save.html).

E7. Use the {supercells} package to create superpixels of similar snow cover monthly values for December 2019. 
Next, apply the `kmeans()` algorithm to derive six categories of superpixels. 
Visualize the results.

E8: Dissolve the borders between superpixels belonging to the same category (hint: see https://geocompr.robinlovelace.net/geometric-operations.html#geometry-unions).
Visualize the results.

E9: Bonus 1: Download elevation data for Germany using the {elevatr} package. 
Visualize the previous results on top of a hillshade map (hint: see https://github.com/Robinlovelace/geocompr/blob/main/code/05-contour-tmap.R).

E10: Bonus 2: Derive clusters of superpixels again, but this time based on a raster time-series of the median (P50) Germany snow cover monthly values for every December between 2000 and 2019.
Visualize the results.