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3. Handling Positive and Negative Values
There are many ways of encoding data that can have positive or negative values on a map or any other visualization. This lesson will introduce some of these methods, and help you determine which one is right for your needs.
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Lesson Goal (00:11)
The goal of this lesson is to learn how to handle positive and negative numbers on maps.
Showing Profit Values (00:24)
Profit is a common value that can be positive or negative. It’s usually represented using color to distinguish between positive and negative and size to identify the value of the profit or loss. An alternative way to show this is to use a two-color gradient, commonly red and black, which replaces both size and color.
If using size and color, the size trait can be adjusted to emphasize positive or negative values as desired. If the smallest points, that is the biggest losses, have the smallest size, then the map will emphasize large profits and large losses will be nearly invisible. If the points closest to zero have the smallest size, then both large profits and large losses will be emphasized.
Another way to emphasize positive values is to remove any color from negative values. Similarly, removing color from positive values allows you to emphasize negative values
Alternative Representations (02:17)
One option to show profit is to use shapes, for example using up arrows for profit and down arrows for losses, with the size of the arrow indicating the level of profit or loss. However, this is generally more difficult to interpret than using color, so we usually want to avoid this.
In the previous lesson, we introduced the map case study and learned how to visualize information on maps.
Our goal in this lesson is to learn how to handle positive and negative numbers on maps.
Let's see how to work with a value like profit that can be positive and negative.
But keep in mind, that it's actually the two traits of size and color working together.
When we want to simplify a visual, try to remove the hardest trait, which is color.
Then gradient can be used instead, and in this case, it also takes the place of size.
It might not seem like a big deal with just this single chart, but when you have multiple images competing on the same page, it makes a difference.
Think of it this way.
When you're reading a page filled with words, like a news story, don't you prefer when the author chooses their words well? To show information like profit, which can have positive and negative values, we have to take a bit more care.
For example, this map shows the highest values, that is the biggest profits with the largest dots, and the lowest values, that is the biggest losses with the smallest dots.
If the smallest values are not as important, then this is a good option.
On the other hand, if you want to make sure that large negative values stand out as much as large positive values, this is better.
Here, big profits and big losses are both represented by large dots, while profit values closer to zero are represented by the smallest dots.
In the first example, Texas was almost invisible.
In the second, we see that it has big losses.
In the same way you have a vocabulary of words to choose, you are building a visual vocabulary.
Let's consider two more views of this map.
As you can see, you can choose to emphasize positive or negative values depending on what you want the reader to focus on.
Let's take the map that emphasizes positive values and use it to dig a little deeper into the hierarchy.
Rather than use color, let's step down the hierarchy to shape.
Up and down arrows are a good choice.
It's a common way people think about positive and negative.
But even with just two shapes, this visual is much harder to work with.
Using a different arrow doesn't help either.
Clearly, replacing color with shape is a bad idea, and this is another example of a visualization type to avoid.
Generally speaking, we always want to stay as close to the top of the hierarchy as possible.
Let's stop the lesson here.
This brings us to the end of our first case study on maps.
We've learned a lot in these lessons about how information should and should not be presented on these common visualizations.
In the next lesson, we'll move on to our second case study and look at how we can improve a stacked bar chart.