Radial stacked bar chart, sorted

Hi dear, I have a problem:

What does mean in angular the sample code:

// Stack the data into series by age
const series = d3.stack()
.keys(d3.union(data.map(d => d.age))) // distinct series keys, in input order
.value(([, D], key) => D.get(key).population) // get value for each series key and stack
(d3.index(data, d => d.state, d => d.age)); // group by stack then series key

Best regads,

This code is using D3.js, a JavaScript library for data visualization, to stack data into series by age. Let’s break it down step by step:

  1. d3.stack(): This function creates a stack layout. Stack layout is a way to represent data where values are stacked on top of each other, typically used in charts like stacked bar charts or area charts.
  2. .keys(d3.union(data.map(d => d.age))): Here, d3.union() is used to get distinct series keys (age values) from the data array. data.map(d => d.age) creates an array of age values from the data objects, and d3.union() ensures that only unique age values are selected.
  3. .value(([, D], key) => D.get(key).population): This line specifies how to access the values for each series key (age) in the data. It uses the value accessor function. The function D.get(key).population is used to retrieve the population value for each age group (key) in the data.
  4. (d3.index(data, d => d.state, d => d.age)): This part of the code groups the data by stacking and series key. It uses d3.index() to create an index of the data based on the specified grouping functions. In this case, the data is grouped first by state and then by age.

Overall, this code is creating a stacked representation of data grouped by age, where each series corresponds to a distinct age group, and the height of each segment in the stack represents the population for that age group.