First Steps on Using R as a GIS

# First Steps on Using R as a GIS
## Introduction
### Stefan Jünger<br>July 08, 2021

---

---

## About This Course

<br>
<br>
This (short) course will teach you how to exploit `R` and apply some of its geospatial techniques.*

By the end of this course, you should...

- be less frightened with using geospatial data in `R`
  - including importing, wrangling, and exploring geospatial data
- be able to create (simple) maps based on your very own processed geospatial data in `R`

.footnote[*Some materials are part of a previous workshop, for which I'd like to thank [Anne-Kathrin Stroppe](https://twitter.com/AStroppe).]

---

## Prerequisites for This Course

.pull-left[
- At least basic knowledge of `R`, its syntax, and internal logic
  - Affinity for using script-based languages
  - Don't be scared to wrangle data with complex structures
- Working versions of `R` (and `Rstudio`) on your computer 
  - Ideally, with the packages installed, I asked you upfront
]

.pull-right[
<br>
<br>
<img src="data:image/png;base64,#C:\Users\mueller2\talks_presentations\esra-workshop-first-steps-R-GIS\content\img\i-love-programming.jpg" width="75%" style="display: block; margin: auto;" />

---

## About Me

.pull-left[
<img src="data:image/png;base64,#C:\Users\mueller2\talks_presentations\esra-workshop-first-steps-R-GIS\content\img\stefan.png" width="50%" style="display: block; margin: auto;" />
]

.pull-right[
- Postdoctoral researcher in the team Data Augmentation at the GESIS department Survey Data Curation
- Ph.D. in social sciences, University of Cologne
]

- Research interests:
  - quantitative methods
  - social inequalities & attitudes towards minorities
  - data management & data privacy
  - reproducible research

.small[
[stefan.juenger@gesis.org](mailto:stefan.juenger@gesis.org) |
[@StefanJuenger](https://twitter.com/StefanJuenger) |
[https://stefanjuenger.github.io](https://stefanjuenger.github.io)
]

---

## About You

.pull-left[
- What's your name?  
- Where do you work/research? What are you working on/researching?
- What is your experience with `R` or other programming languages?
- Do you already have experience with geospatial data?
]

.pull-right[
<br>
<img src="data:image/png;base64,#C:\Users\mueller2\talks_presentations\esra-workshop-first-steps-R-GIS\content\img\so-tell-me-5be02d.jpg" width="800" style="display: block; margin: auto;" />
.tinyisher[.center[[Source](https://makeameme.org/meme/so-tell-me-5be02d)]]
]
- **What do you want to use `R` and geospatial data for?**

---

## Preliminaries
<br>
<br>
- The workshop consists of a combination of a few lectures and hands-on exercises
- Feel free to ask questions at any time
- Slides and other materials are available at:

---

## Course Schedule

<table class="table" style="margin-left: auto; margin-right: auto;">
 <thead>
  <tr>
   <th style="text-align:left;"> Time </th>
   <th style="text-align:left;"> Title </th>
  </tr>
 </thead>
<tbody>
  <tr>
   <td style="text-align:left;"> 01:00pm-01:20pm </td>
   <td style="text-align:left;"> Introduction </td>
  </tr>
  <tr>
   <td style="text-align:left;"> 01:20pm-01:30pm </td>
   <td style="text-align:left;"> Exercise 1: R Warm up </td>
  </tr>
  <tr>
   <td style="text-align:left;"> 01:30pm-02:00pm </td>
   <td style="text-align:left;"> Data Processing &amp; Spatial Linking </td>
  </tr>
  <tr>
   <td style="text-align:left;"> 02:00pm-02:30pm </td>
   <td style="text-align:left;"> Exercise 2: Geospatial Data Wrangling </td>
  </tr>
  <tr>
   <td style="text-align:left;"> 02:30pm-02:45pm </td>
   <td style="text-align:left;"> Break </td>
  </tr>
  <tr>
   <td style="text-align:left;"> 02:45pm-03:15pm </td>
   <td style="text-align:left;"> Easy Maps </td>
  </tr>
  <tr>
   <td style="text-align:left;"> 03:15pm-03:45pm </td>
   <td style="text-align:left;"> Excercise 3: Build your own map </td>
  </tr>
  <tr>
   <td style="text-align:left;"> 03:45pm-04:00pm </td>
   <td style="text-align:left;"> Closing, Q &amp; A </td>
  </tr>
</tbody>
</table>

---

## Now

<table class="table" style="margin-left: auto; margin-right: auto;">
 <thead>
  <tr>
   <th style="text-align:left;"> Time </th>
   <th style="text-align:left;"> Title </th>
  </tr>
 </thead>
<tbody>
  <tr>
   <td style="text-align:left;background-color: yellow !important;"> 01:00pm-01:20pm </td>
   <td style="text-align:left;background-color: yellow !important;"> Introduction </td>
  </tr>
  <tr>
   <td style="text-align:left;"> 01:20pm-01:30pm </td>
   <td style="text-align:left;"> Exercise 1: R Warm up </td>
  </tr>
  <tr>
   <td style="text-align:left;"> 01:30pm-02:00pm </td>
   <td style="text-align:left;"> Data Processing &amp; Spatial Linking </td>
  </tr>
  <tr>
   <td style="text-align:left;"> 02:00pm-02:30pm </td>
   <td style="text-align:left;"> Exercise 2: Geospatial Data Wrangling </td>
  </tr>
  <tr>
   <td style="text-align:left;"> 02:30pm-02:45pm </td>
   <td style="text-align:left;"> Break </td>
  </tr>
  <tr>
   <td style="text-align:left;"> 02:45pm-03:15pm </td>
   <td style="text-align:left;"> Easy Maps </td>
  </tr>
  <tr>
   <td style="text-align:left;"> 03:15pm-03:45pm </td>
   <td style="text-align:left;"> Excercise 3: Build your own map </td>
  </tr>
  <tr>
   <td style="text-align:left;"> 03:45pm-04:00pm </td>
   <td style="text-align:left;"> Closing, Q &amp; A </td>
  </tr>
</tbody>
</table>

---

## What Are Geospatial Data?

.pull-left[
Data with a direct spatial reference `\(\rightarrow\)` **geo-coordinates**
- Information about geometries
- Optional: Content in relation to the geometries

Can be projected jointly in one single space
- Allows data linking and extraction of substantial information
]

.pull-right[
<img src="data:image/png;base64,#C:\Users\mueller2\talks_presentations\esra-workshop-first-steps-R-GIS\content\img\fig_geometries.png" width="85%" style="display: block; margin: auto;" />

.tinyisher[Sources: OpenStreetMap / GEOFABRIK (2018), City of Cologne (2014), and the Statistical Offices of the Federation and the Länder (2016) / Jünger, 2019]
]

---

## Geospatial Data in This Course

In the folder called `./data` in the same folder as the other materials for this workshop, you can find the data files prepped for all the exercises and slides.

- Covid-19 cases for Cologne across the city's districts available at the [Open Data Portal of Cologne](https://www.offenedaten-koeln.de/dataset/corona-fallzahlen-koeln)
- Hospital locations in Cologne are also distributed via the [Open Data Portal of Cologne](https://www.offenedaten-koeln.de/dataset/krankenh%C3%A4user-k%C3%B6ln)
- Cologne's road network; [guess from where](https://www.offenedaten-koeln.de/dataset/strasse)
- Number of immigrants and inhabitants from German Census 2011 data are provided by the [Federal Statistical Office Germany, Wiesbaden 2020](https://www.zensus2011.de/EN/Home/home_node.html)

**Please make sure that if you reuse any of the provided data to cite the original data sources.**

---

## What Is GIS?

Most common understanding: Geographic Information Systems (GIS) as specific software to process geospatial data for 
- Visualization
- Analysis

---

## Data Specifics

.pull-left[
</br>
</br>
<img src="data:image/png;base64,#C:\Users\mueller2\talks_presentations\esra-workshop-first-steps-R-GIS\content\img\fig_3d_simple.png" width="9083" style="display: block; margin: auto;" />

Coordinate reference systems (CRS)
- Allow the projection on earth's surface
- Differ in precision for specific purposes
]

---

## Layers Must Match!

---

## Types of CRS

<br>
.pull-left[
**Projected CRS**
- projection of geometries on a flat surface (planar)
- distance between two points is a straight line
]

.pull-right[
**Geographic CRS**
- (unprojected) description of specific points on a sphere
- distance between two points is a bent line
]

<br>
(There are also geocentric CRS requiring a z-coordinate...)

---

---

## CRS Definitions

Old Standard: `PROJ.4` Strings

```
+proj=laea +lat_0=52 +lon_0=10 +x_0=4321000 +y_0=3210000 +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs 
```

New Kid in Town: `WKT` (“Well Known Text”)

.small[
```
PROJCS["ETRS89 / LAEA Europe",
    GEOGCS["ETRS89",
        DATUM["European_Terrestrial_Reference_System_1989",
            SPHEROID["GRS 1980",6378137,298.257222101,
                AUTHORITY["EPSG","7019"]],
            TOWGS84[0,0,0,0,0,0,0],
            AUTHORITY["EPSG","6258"]],
        PRIMEM["Greenwich",0,
            AUTHORITY["EPSG","8901"]],
        UNIT["degree",0.0174532925199433,
            AUTHORITY["EPSG","9122"]],
        AUTHORITY["EPSG","4258"]],
    PROJECTION["Lambert_Azimuthal_Equal_Area"],
    PARAMETER["latitude_of_center",52],
    PARAMETER["longitude_of_center",10],
    PARAMETER["false_easting",4321000],
    PARAMETER["false_northing",3210000],
    UNIT["metre",1,
        AUTHORITY["EPSG","9001"]],
    AUTHORITY["EPSG","3035"]]
```
]

---

## EPSG Codes

.pull-left[
Eventually, it's not as challenging to work with CRS in `R` as it may seem
- we don't have to use PROJ.4 or WKT strings directly.

Most of the times it's enough to use so-called EPSG Codes ("European Petroleum Survey Group Geodesy")
- Small digit sequence
]

.pull-right[
<br>
<img src="data:image/png;base64,#C:\Users\mueller2\talks_presentations\esra-workshop-first-steps-R-GIS\content\img\ImageEPSGlogo.gif" style="display: block; margin: auto;" />
.tinyisher[.center[[Source](http://geotiff.maptools.org/proj_list/guid7.html)]]
]

---

## More Details on Geospatial Data

Let's learn about geospatial data as we learn about specific formats:
- vector data 
- raster data

.pull-left[
<img src="data:image/png;base64,#C:\Users\mueller2\talks_presentations\esra-workshop-first-steps-R-GIS\content\img\Raster-and-Vector-data-types-as-representative-of-real-world-geographic-space_W640.jpg" width="75%" style="display: block; margin: auto;" />

.pull-right[
Be assured: `R` can serve as a full-blown Geographic Information System (GIS) for all these different data types.
]

---

## `R` Packages for Geospatial Data

There have been packages for geospatial data in `R` already for a long time.

.pull-left[
- [`sp`](https://cran.r-project.org/web/packages/sp/index.html) for vector data
- [`raster`](https://cran.r-project.org/web/packages/raster/index.html) for raster data
  - the successor: [`terra`](https://cran.r-project.org/web/packages/terra/index.html)

Cutting-edge for vector data and raster data (cubes)
- [`sf`](https://cran.r-project.org/web/packages/sf/index.html)
- [`stars`](https://r-spatial.github.io/stars/)
]

.pull-right[
<br>
<img src="data:image/png;base64,#C:\Users\mueller2\talks_presentations\esra-workshop-first-steps-R-GIS\content\img\sf.jpg" width="80%" style="display: block; margin: auto;" />

---

## Packages in This Course

We will use plenty of different packages during the course, but only a few are our main drivers (e.g., the `sf` package). Here's the list of packages

- [`dplyr`](https://cran.r-project.org/web/packages/dplyr/index.html)
- [`mapview`](https://cran.r-project.org/web/packages/mapview/index.html)
- [`sf`](https://cran.r-project.org/web/packages/sf/index.html)
- [`stars`](https://cran.r-project.org/web/packages/stars/index.html)
- [`tmap`](https://cran.r-project.org/web/packages/tmap/index.html)
- [`tmaptools`](https://cran.r-project.org/web/packages/tmaptools/index.html)

*Note*: Some additional packages will be installed as dependencies.

---

## What You'll See During the Course: Piping In `R`

Usually, in `R` we apply functions as follows:

```r
f(x)
```

In the logic of pipes this function is written as:

```r
x %>% f(.)
```

We can use pipes on more than one function:

```r
x %>% 
  f_1() %>% 
  f_2() %>% 
  f_3()
```

More details: https://r4ds.had.co.nz/pipes.html

---

[Exercise](https://stefanjuenger.github.io/esra-workshop-first-steps-R-GIS/exercises/1_R_Warm_Up.html)

[Solution](https://stefanjuenger.github.io/esra-workshop-first-steps-R-GIS/solutions/1_R_Warm_Up.html)

---

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background-size: cover

.left-column[
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<img src="data:image/png;base64,#C:\Users\mueller2\talks_presentations\esra-workshop-first-steps-R-GIS\content\img\stefan.png" width="90%" style="display: block; margin: auto;" />
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