Bell curve

A bell curve series is a graphical representation of a normal (Gaussian) probability distribution. Bell curve is used to visualize the probability of occurring outcomes. The curve is bell-shaped, and its center top point is the mean of the base data. The module modules/histogram-bellcurve.js is required for this chart.

For more detailed samples and documentation check the API.

Click here to check the code.

Prerequisites for a good visualization

To implement this chart type properly, there are a few assumptions that must be met:

  1. The input data must be one-dimensional. The chart describes a statistical attribute of one attribute. Visualizing the normal distribution of multiple attributes requires multiple series.

  2. The chart assumes an underlying normal distribution in the data. The chart type will derive a normal distribution from any data, but if the data itself is not normally distributed, the visualization becomes misleading and wrong.

How to create a Bell Curve based on Derived Data

The bell curve series is an areaspline series with self-setting data. The data property can be substituted by a base series (more precisely y values of the data).

Two steps are required to create a bell curve:

  1. Set the series type to bellcurve.

  2. Set baseSeries to the right data series’ id or index.

series: [{
    type: 'bellcurve',
    xAxis: 1,
    yAxis: 1,
    baseSeries: 1
}, {
    data: [3.5, 3, 3.2, 3.1, 3.6, 3.9, 3.4]
}]

Setting the Bell Curve

A bell curve series has two additional options:

  • intervals: to control the length of the curve.
  • pointsInInterval: to control the number of points within one interval, i.e., the number of points between σn and σn+1.

The following demo visualizes four intervals for each side of the bell curve, and five points between each Nxσ:

series: [{
    type: 'bellcurve',
    intervals: 4,
    pointsInInterval: 5
    ...
}]

Click here to check the code.

The black markers indicate the borders of the intervals - four intervals for each side of the curve. Within one interval there are four markers plus the border black marker. On the left side intervals are left-closed, on the right side right-closed. The interval length is the bell curve’s standard deviation.

Additionally, there is one point at the top which is the mean of the bell curve.

Edit this page