CODEWITHSUNDEEP
d3.js
Jimmy Chen
Jimmy Chen

Reputation: 29

How to find min and max value in a array of objects

I am new to D3 and Javascript community. I have an array of objects(countries) and each object consists of years represented by key and its value(incomes).

How to get the minimum and maximum value of incomes across all the objects and its key to set the color legend?

Please find the link https://observablehq.com/d/287af954b6aaf349 of the project, hope it would help to explain the question.

Thank you for reading the questions.

Upvotes: 1

Views: 962

Answers (2)

Ricardo Sanchez
Ricardo Sanchez

Reputation: 5167

Another useful method backed in d3 is the d3.extent() function check this article

Upvotes: 1

Ruben Helsloot
Ruben Helsloot

Reputation: 13129

To get the global maximum, you can use

const max = d3.max(
    countries.map(country =>
        d3.max(Object.values(country))));

// 179000

What it does is iterate over the countries, grabbing from each country the maximum of all the values. Then, it takes the maximum of these maxima and returns that.

To also get the corresponding year, it becomes more complex. You can use Object.entries to get the key value pair, instead of just the value. You can then manually loop over each country, updating the max value, and the corresponding year as you go

data.reduce((max, country) => {
  const newMax = d3.max(Object.values(country));
  if(newMax > max.value) {
    return {
      year: Object.entries(country).find(([year, value]) => value === newMax)[0],
      value: newMax,
    };
  }
  return max;
}, {value: 0});

// {year: "2040", value: 179000}

Upvotes: 2

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