Cumulative sum of values belonging to a same field in an array

Question

I have an array in the following format that has x and y values with a data field and I am looking to convert into an array that adds up all the individual value over a specific data, and then shows a cumulative value (summing over that date and then adding the value to the previous dates). Eg.

data_array = [
{xvalue: 10, yvalue: 5, date: "12/2"},
{xvalue: 10, yvalue: 5, date: "12/2"},
{xvalue: 8, yvalue: 3, date: "12/3"},
{xvalue: 10, yvalue: 5, date: "12/3"},
{xvalue: 6, yvalue: 1, date: "12/4"},
{xvalue: 20, yvalue: 3, date: "12/4"},
]

New array

new_data = [
{xvalue: 20, yvalue: 10, date: "12/2"}
{xvalue: 38, yvalue: 18, date: "12/3"}
{xvalue: 64, yvalue: 22, date: "12/4"}
]

What will be a way to do this efficiently? Currently I have the following way that works but feel like its not the best implementation

var temp = {}
var obj = null
for (var i=0; i<data_array.length; i++){
    obj = data_array[i];

    if (!temp[obj.date]) {
        temp[obj.date]=obj;
    } 
    else {
        temp[obj.date].xvalue += obj.xvalue;
        temp[obj.date].yvalue += obj.yvalue
    }
}
var result = [];
for (var prop in temp){
    result.push(temp[prop]);
}
console.log("result", result)

for (var i=0; i< result.length; i++){
  if (i!=0){
    result[i].xvalue +=result[i-1].xvalue;
    result[i].yvalue +=result[i-1].yvalue;
  }
}

Does this answer your question? [Sum javascript object propertyA values with same object propertyB in array of objects](https://stackoverflow.com/questions/19233283/sum-javascript-object-propertya-values-with-same-object-propertyb-in-array-of-ob) — AZ_, Dec 30 '19 at 08:30
[Sum similar keys in an array of objects](https://stackoverflow.com/questions/24444738) — adiga, Dec 30 '19 at 08:32
Hi everyone - I updated my implementation but would love some feedback if there is a better way to do this — zeroanthem86, Dec 30 '19 at 09:11

Geetanjali · Answer 1 · 2019-12-30T08:54:36.987

3

data_array = [
{xvalue: 10, yvalue: 5, date: "12/2"},
{xvalue: 10, yvalue: 5, date: "12/4"},
{xvalue: 8, yvalue: 3, date: "12/3"},
{xvalue: 10, yvalue: 5, date: "12/2"},
{xvalue: 6, yvalue: 1, date: "12/3"},
{xvalue: 20, yvalue: 3, date: "12/2"},
];
var reduced =  data_array.reduce(function(final,item){
  if(final[item.date]){
    final[item.date] = {cummxvalue: item.xvalue+final[item.date].cummxvalue, cummyvalue: item.yvalue+final[item.date].cummyvalue, date: item.date};
  }else{
    final[item.date] = {cummxvalue: item.xvalue, cummyvalue: item.yvalue, date: item.date};
  }
return final;
},{});
var new_data = Object.values(reduced);
console.log(new_data);

edited Dec 30 '19 at 08:54

answered Dec 30 '19 at 08:44

Geetanjali

458
3
13

may I suggest using the `Object.values(reduced)`, instead of the for-loop at the end? – Dor Lugasi-Gal Dec 30 '19 at 08:52
Thanks @Geetanjali! I updated my question with my implementation as I also need to do cumulative sum over the date. Thoughts on that implmentation? – zeroanthem86 Dec 30 '19 at 09:15

Addis · Answer 2 · 2019-12-30T13:01:10.580

You may loop through the array and add xvalues and yvalue, and copy into a new array as you go if the elements donot have the same date value. You will also need to sort the array incase it's not already sorted as your first example.

const data_array = [
  {xvalue: 10, yvalue: 5, date: "12/2"},
  {xvalue: 10, yvalue: 5, date: "12/4"},
  {xvalue: 8, yvalue: 3, date: "12/3"},
  {xvalue: 10, yvalue: 5, date: "12/2"},
  {xvalue: 6, yvalue: 1, date: "12/3"},
  {xvalue: 20, yvalue: 3, date: "12/2"}
]

let new_data = [];
let cummxvalue = 0;
let cummyvalue = 0;

data_array.sort( (a, b) => a.date > b.date );

for( const obj of data_array) {
  let o = new_data.find(o => o.date === obj.date);
  cummxvalue += obj.xvalue;
  cummyvalue += obj.yvalue;

  if(!o) {
    new_data.push({cummxvalue: cummxvalue, cummyvalue: cummyvalue, date: obj.date});
  }
  else {
    o.cummxvalue = cummxvalue;
    o.cummyvalue = cummyvalue;
  }
}

console.log(new_data)

Cumulative sum of values belonging to a same field in an array

2 Answers2