CODEWITHSUNDEEP
javascriptarraysd3.js
Vasilescu Catalin
Vasilescu Catalin

Reputation: 17

d3.js How to get sum of array of objects data?

I have the csv file 

DATE OF ARREST, ARREST RESOLUTION, COUNT
01/01/1988, BONDED OUT, 1
01/01/1988, BONDED OUT, 1
01/01/1988, BONDED OUT, 1
02/01/1988, BONDED OUT, 1
02/01/1988, BONDED OUT, 1

I want to create a chart view with the data above. To do this, I have to sum "COUNT" for each date. For example, I need to have 01/01/1988, BONDED OUT, 3 ... in this day I have 3 cases. To parse the date I use 

var parseDate = d3.timeParse("%m/%d/%Y");

 data.forEach(
  function(d){
  d.count = +d["COUNT"];
  d.date = parseDate(d["DATE OF ARREST"]);
})

The chart shows the year correctly, but the number of cases is always 1. How can I count the "COUNT" for each year?

Upvotes: 0

Views: 1041

Answers (1)

Mikhail Shabrikov
Mikhail Shabrikov

Reputation: 8509

If I understand you correctly, you want to convert your data and sum all COUNT for the same day. You can do it with d3.nest.

var dataAsCsv = `DATE OF ARREST,ARREST RESOLUTION,COUNT
01/01/1988,BONDED OUT,1
01/01/1988,BONDED OUT,1
01/01/1988,BONDED OUT,1
02/01/1988,BONDED OUT,1
02/01/1988,BONDED OUT,1`;

var data = d3.csvParse(dataAsCsv);

var parseDate = d3.timeParse("%m/%d/%Y");

var convertedData = d3.nest()
  .key(function(d) { return d["DATE OF ARREST"]; })
  .rollup(function(v) {
      return {
        date: parseDate(v[0]["DATE OF ARREST"]),
        count: d3.sum(v, function(d) { return +d["COUNT"]; })
      }
  })
  .entries(data).map(function(d) { return d.value});

console.log(convertedData);
<script src="https://d3js.org/d3.v4.min.js"></script>

Upvotes: 1

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