The ‘scaleThreshold()’ Scale

We are going to be exploring one more scale called the threshold scale. The threshold scale is more customizable than the previous three scales we have been using. Up until now, D3 has done the work for calculating how big a bucket is. It did not let us set the size of a bucket. The threshold scale allows us to configure how data is distributed. Let’s explore how the threshold scale works.

How a threshold scale works

The threshold scale will transform continuous data into discrete data. It is the same as the quantize and quantile scales. We are going to be using this scale to transform the data into three colors. The colors will again be white, pink, and red.

Before we proceed further, we should discuss what the word threshold means. A threshold is a level, rate, or amount at which something comes into effect.

Thresholds are commonly used for a lot of things. For example, a speed limit is considered a threshold. If a sign says you can not drive faster than 60 miles per hour, the threshold would be 60. Going faster than 60 miles per hour will result ...