Mapping California Colleges

1. Mapping a State's Colleges

Now that we have a general sense of the data we are working with, let's dive in and take a closer look at all of the colleges in one state. As an example, we'll create a subset of the IPEDS data with only colleges in Maine to plot on a leaflet map.

2. How many 4-year colleges are there in Maine?

How many four-year colleges do you think there are in Maine, a state with approximately 1-dot-3 million residents compared to California's nearly 40 million? To figure out the answer, we can filter the IPEDS data to the observations that have a state value of ME, which is the common abbreviation used for Maine in the United States. This gives us a tibble with 21 rows, telling us that there are 21 four-year colleges in Maine. Perhaps, a more interesting question is how are these 21 colleges distributed throughout the state? Let’s make a map to find out.

3. Mapping a State's Colleges

When we pass our data on Maine's colleges to addMarkers, leaflet tells us that it has automatically identified the variables that represent our coordinates. Using these coordinates, leaflet creates a map that is zoomed out to Maine by default and reveals that 19 of Maine's 21 four-year colleges are in the southern half of the state. This clustering of colleges leads to some overlapping of the pin markers. You can imagine how this might look in a state with more colleges, like California.

4. Mapping a State's Colleges

When we make maps with markers that are clustered together, the pin markers rendered by addMarkers() can overlap and obscure our data. One alternative is to use the addCircleMarkers() function. Why are the pin markers still showing up on our map? Remember, each set of markers are their own layer, so adding a new set will not replace the existing ones.

5. Mapping a State's Colleges

Often it is desirable to add different types of markers to a map to identify different types of data, however this is not one of those times, so we need to clear the pins prior to adding the circle markers. This approach renders a map with blue circle markers with a radius of 3 pixels representing the locations of Maine's 21 four-year colleges.

6. Mapping a State's Colleges

We can customize several aspects of our circle markers. For example, we can control the radius and the color of the circles. We can also retain our pop-ups when using circle markers.

7. Let's practice!

Now it's your turn to apply what we've learned about Maine to create a map of the nearly 300 colleges in California.

Interactive Maps with leaflet in R

BeginnerSkill Level

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Chapter 1 will introduce students to the htmlwidgets package and the leaflet package. Following this introduction, students will build their first interactive web map using leaflet. Through the process of creating this first map students will be introduced to many of the core features of the leaflet package, including adding different map tiles, setting the center point and zoom level, plotting single points based on latitude and longitude coordinates, and storing leaflet maps as objects. Chapter 1 will conclude with students geocoding DataCamp’s headquarters, and creating a leaflet map that plots the headquarters and displays a popup describing the location.

Exercise 1: Introduction to leaflet Exercise 2: Loading the leaflet Library Exercise 3: Creating an Interactive Web Map Exercise 4: Map Tiles Exercise 5: Provider Tiles Exercise 6: Adding a Custom Map Tile Exercise 7: Setting the Default Map View Exercise 8: A Map with a View I Exercise 9: A Map with a Narrower View Exercise 10: Plotting DataCamp HQ Exercise 11: Mark it Exercise 12: Adding Popups and Storing your Map

In Chapter 4 students will learn to map polygons, which can be used to define geographic regions (e.g., zip codes, states, countries, etc.). Chapter 4 will start by plotting the zip codes in North Carolina that fall in the top quartile of mean family incomes. Students will learn to customize the polygons with color palettes and labels. Chapter 4 will conclude with adding a new layer to the map of every college in America that displays every zip code with a mean income of $200,000 or more during the 2015 tax year. Through the process of mapping zip codes students will learn about spatial data generally, geoJSON data, the @ symbol, and the addPolygons() function. Furthermore, students will have an opportunity to practice applying many of the options that they learned about in the previous chapters, such as popups and labels, as well as new ways to customize their maps, such as the highlight option in addPolygons().

Exercise 1: Spatial Data Exercise 2: Introduction to Spatial Data Exercise 3: Exploring Spatial Data Exercise 4: Joining Spatial Data Exercise 5: Mapping Polygons Exercise 6: addPolygons() Function Exercise 7: NC High Income Zips Exercise 8: addPolygon() Options Exercise 9: Let's do some Logging Exercise 10: Putting it All Together Exercise 11: Wealthiest Zip Codes in America Exercise 12: Final Map Exercise 13: Thank you!