Combine array of values with array of dates while averaging values for duplicate dates-CodePudding

I can't work out the logic on this one, most of the other questions I've found have different data structures such as arrays of objects with duplicate keys.

I have two arrays of equal length - one is a list of values, the other is a corresponding date. For example:

values = [100,100,95,80,100,100,87,88,90,40];
dates = ['03 Dec', '03 Dec', '04 Dec', '04 Dec', '04 Dec', '04 Dec', '05 Dec', '05 Dec', '06 Dec', '06 Dec'];

The real arrays are much longer, circa 1,000 values with corresponding dates spanning 10 days. I am trying to get the average value for each date to make it much easier to display using apexcharts.

What I am trying to get to is something like this:

values = [100,93.75,87.5,65];
dates = ['03 Dec', '04 Dec', '05 Dec', '06 Dec'];

or indeed:

{03 Dec: '100', 04 Dec: '93.75', 05 Dec: '87.5', 06 Dec: '65'}

I've tried to combine with dates.reduce but I'm stuck with how to average the values for each day.

Any pointers would be gratefully received. Thank you.

CodePudding user response：

Try the following code. It results in an object with the dates as properties and the averages as corresponding values:

var values = [100,100,95,80,100,100,87,88,90,40];
var dates = ['03 Dec', '03 Dec', '04 Dec', '04 Dec', '04 Dec', '04 Dec', '05 Dec', '05 Dec', '06 Dec', '06 Dec'];
var averages={};
var lastdate="",total,count;
dates.forEach( (currentValue, index, )=>{
    if (currentValue !== lastdate) {
        if (lastdate !== "") {
            averages[lastdate] = total/count;
        }
        lastdate=currentValue;
        total=0;
        count=0;
    }
    total  = values[index];
    count  ;
})
averages[lastdate] = total/count;
console.log(averages);

CodePudding user response：

This should work. See comments in code for explanation, ended up making more sense that way.

const values = [100,100,95,80,100,100,87,88,90,40];
const dates = ['03 Dec', '03 Dec', '04 Dec', '04 Dec', '04 Dec', '04 Dec', '05 Dec', '05 Dec', '06 Dec', '06 Dec'];

const result = {};

for (let i = 0; i < dates.length; i  ) {
  const date = dates[i];

  if (!result[date]) {
    // create a property in the object with the current date and set it to the sum of the values that match the current date
    result[date] = values.filter((value, index) => dates[index] === date).reduce((total, value) => total   value, 0);
  }
}

for (const date in result) {
  // Divide the sum of values for the current date by the number of values that match the current date
  result[date] /= values.filter((value, index) => dates[index] === date).length;
}

console.log(result);