Calculate average of array of objects with filtering for undefined

Question

I am trying to calculate the average of values with the same key in a array of objects. Not all the Objects consist of the same values as the other but I still want the average returned depending on how many times it appears in the array. For example I want

const Object1 = [{
  2005: 5.6,
  2006: 5.2
}, {
  2005: 5.6,
  2006: 5.7,
  2007: 5.4
}, {
  2005: 5.6,
  2006: 5.9,
  2007: 5.8
}]

To return

{
  2005: 5.599999999999999,
  2006: 5.6000000000000005,
  2007: 5.6
}

This is what I have tried so far. Right now the problem is that I have no way to / it by the amount of times it appears. And if it is missing the year the value becomes undefined and this causes the result to be NaN.

const Object1 = [{
  2005: 5.6,
  2006: 5.2
}, {
  2005: 5.6,
  2006: 5.7,
  2007: 5.4
}, {
  2005: 5.6,
  2006: 5.9,
  2007: 5.8
}]
const years = Object.keys(Object.assign({}, ...Object1));
const Result = years.reduce((a, v) => ({
  ...a,
  [v]: v
}), {})
console.log(Result)
years.map((year) => {

  const value =
    Object1.map(function(obj) {
      return obj[year]
    }).reduce(function(a, b) {
      return (a + b)
    }) / years.length
  Result[year] = value
})
console.log(Result)

hgb123 · Accepted Answer · 2022-04-21 03:25:42Z

2

You could group points by year and calculate points solely based on each group

const object1 = [
  {
    2005: 5.6,
    2006: 5.2,
  },
  {
    2005: 5.6,
    2006: 5.7,
    2007: 5.4,
  },
  {
    2005: 5.6,
    2006: 5.9,
    2007: 5.8,
  },
];

const groupPointByYears = object1.reduce((map, obj) => {
  for (const [year, point] of Object.entries(obj)) {
    if (!map.has(year)) {
      map.set(year, []);
    }
    map.get(year).push(point);
  }

  return map;
}, new Map());

console.log(Array.from(groupPointByYears));

const res = Object.fromEntries(
  Array.from(groupPointByYears).map(([year, points]) => [
    year,
    points.reduce((sum, point) => sum + point, 0) / points.length,
  ])
);

console.log(res);

answered Apr 21, 2022 at 3:25

hgb123

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1 Comment

Running moments Over a year ago

Out of the 3 suggestions I have gotten you think this is the best one? @hgb123

may · Accepted Answer · 2022-04-21 03:41:57Z

2

const years = Object1.reduce(( prev, curr ) => {
    for (const key in curr) prev[key] = (prev[key] || []).concat(curr[key])
    return prev
}, {})

const Result = {}
for (const year in years) {
    Result[year] = years[year].reduce(( prev, val ) => prev + val, 0) / years[year].length
}

console.log(Result)

this code first puts all values of every year in an array in an object (that's what the first reduce does) then it loops over every year and adds the average (sum of all values divided by the amount of values) to the Result object

edited Apr 21, 2022 at 3:41

answered Apr 21, 2022 at 3:19

may

378 bronze badges

3 Comments

Running moments Over a year ago

I like this answer alot, However lets say I were to add one more nested Object and than put the years into that. Like this

const Object1 = [{     Male: {       2005: 5.6,       2006: 5.2,     },     Female: {       2005: 5.6,       2006: 5.4,     }   },   {     Male: {       2005: 5.9,       2006: 5.2,       2007: 5.3     },     Female: {       2005: 5.6,       2006: 5.4,       2007: 5.9,     }   },   {     Male: {       2005: 5.9,       2006: 5.2,       2007: 5.3     },     Female: {       2005: 5.2,       2006: 5.9,       2007: 5.1,     }  } ];

Running moments Over a year ago

How Would i make that return {Male:{2017:5.55, etcc.}, Female:{2017...}}

may Over a year ago

well you would have to loop over the object, like i did in the first one, to group them by "male" and "female" and then loop over "male" and "female" and just do exactly what i did. that is almost an entirely new question, do you still need me to edit my answer to include a code snippet to solve this or have you figured out a way?

yilishabai · Accepted Answer · 2022-04-21 07:32:53Z

2

I made some changes based on your code

const Object1 = [{
  2005: 5.6,
  2006: 5.2
}, {
  2005: 5.6,
  2006: 5.7,
  2007: 5.4
}, {
  2005: 5.6,
  2006: 5.9,
  2007: 5.8
}]
const years = Object.keys(Object.assign({}, ...Object1));
const Result = years.reduce((a, v) => ({
  ...a,
  [v]: v
}), {})
console.log(Result)
years.map((year) => {
 // Filter out keywords while removing undefined ones
  var filteredYear = Object1.map(function(obj) {
      return obj[year]
    }).filter(e=>e!=undefined)
 // Perform a reduce calculation with the filtered results
  const value =
  filteredYear.reduce(function(a, b) {
      return (a + b)
    }) / filteredYear.length
  Result[year] = value
})
console.log(Result)

edited Apr 21, 2022 at 7:32

answered Apr 21, 2022 at 3:20

yilishabai

363 bronze badges

1 Comment

Cristik Over a year ago

Your answer could be improved with additional supporting information. Please edit to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers in the help center.

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