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How to Smart Map: Relationships

Map two attributes from your data within a single map in ArcGIS Online

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This quick guide introduces how to easily make a map that compares two different topics.

What is a Relationship Map?

Relationship maps are an easy way to visualize and compare multiple attributes from your data within ArcGIS Online. 

These maps allow you to explore the relationship between two topics within a single map and help you see if they are possibly related. This new mapping option is easy to try, and can provide valuable insight about your data that you may not have found otherwise. 

So what is a relationship map?

A relationship map combines two data patterns to see if they converge geographically. For example, here is a choropleth map showing the percentage of diabetes in the US by county.

Here, we have another thematic choropleth map showing the percent of the population classified as obese:


At a glance, these patterns look similar, but I want to see where the patterns are both high, both low, or occurring strongly on their own. Relationship mapping allows me to combine these two map patterns in order to explore where patterns overlap or diverge. So if we combine these two color ramps to show a combination of the patterns, we would get a grid and map like this:

The two schemes converge, allowing us to explore where attributes may or may not be related.

From this map, we see that the corners tell us a great deal of information. The purple values show where high rates of both obesity and diabetes. The darkest pink values show where there is a high amount of diabetic population, but fewer people with obesity. The darkest blue values show where people are most likely to be obese, but less likely to have diabetes. 

This type of map is valuable, especially when exploring your data. It can help you quickly assess if two attributes might be related. 

Classically known as a bivariate choropleth map, these maps have always been possible within ArcGIS, but with a great deal of customization and forethought. Now, you can create these maps in minutes, and can easily make adjustments while you explore the data. Using Cindy Brewer-inspired color ramps, these bivariate choropleth maps show how two data patterns overlap (or don't overlap).  To learn more about this mapping style and to see examples, visit this blog.

So how are these maps made today? 

It's as easy as selecting the two attributes you want to compare!

How to Make a Relationship Map

In Map Viewer within ArcGIS Online, bring your point, line, or polygon feature service into the map. Within the Change Style layer option, select two numeric (number) attributes from your data that you are interested in seeing on the map. Smart mapping will automatically recognize that you have selected two numbers, and within your list of mapping styles, select the “Relationship” mapping style.

If you're new to the Change Style settings in ArcGIS Online, you can also circle back to this "How to Smart Map" Story Map to learn the basics.

Let's step through the creation of a relationship map to see how it is done:

This is just an introduction to the options that can be used for relationship mapping. We always encourage you to go beyond the default settings in order to tune the map to the topic you are interested in making.

For example, below is a map that uses the relationship style to show hurricane paths from 1924 to 2014. Hurricanes are the strongest when pressure is low and wind speed is high. This is shown in this map using pink. To emphasize the strongest part of the hurricanes, I rotated the legend using the "Focus" adjustment. I also used custom labels to help explain what is being seen on the map.

There are many different ways to easily create customized maps using the "Relationship" and "Relationship and Size" mapping styles. However, you can also use these styles as a way to easily explore your data. Simply select your attributes and the mapping style, and see if you find something new about your data. 

Additional Resources

There are many other additional resources to help you get started with the relationship mapping style: 

- What is a  Relationship Map? (blog)

- How to Make a Relationship Map in ArcGIS Online (blog) 

- ArcGIS Online Help Pages

- Relationship map examples (links at the end of this Story Map)

Don't be afraid to try this mapping style with your point, line, and polygons datasets.  Just select the two attributes you want to explore, and you're on your way.

Happy Mapping!

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