Loop through an array to find the average values of different segments within the array

I am currently working with an array structured like this:

["2011-06-16 16:37:20",23.2],
["2011-06-21 16:37:20",35.6],
["2011-06-26 16:37:20",41.8],
["2011-07-01 16:37:20",25],
["2011-07-06 16:37:20",22.8],
["2011-07-11 16:37:20",36.4],
["2011-07-16 16:37:20",34],
["2011-07-21 16:37:20",20]
[...]

Format: [$date,count]

My task now is to enhance each element of the array with a 3rd and 4th value, which are calculated as averages of N counts before or after.

For instance, when N=3

The 3rd value should be the average of the 3 count-values preceding, and the 4th value should be the average of the 3 count-values succeeding the current array element. The resulting array will look like this:

["2011-06-16 16:37:20",23.2, null,  34.13],
["2011-06-21 16:37:20",35.6, null,  29.86],
["2011-06-26 16:37:20",41.8, null,  28.06],
["2011-07-01 16:37:20",25,   33.53, 31.06],
["2011-07-06 16:37:20",22.8, 34.13, 30.13],
["2011-07-11 16:37:20",36.4, 29.86, null],
["2011-07-16 16:37:20",34,   28.06, null],
["2011-07-21 16:37:20",20,   31.06, null]

The null value is a placeholder for cases where averages cannot be calculated due to insufficient data points. In such cases, the average of all available counts can be displayed instead, like "24.4" (23.2+35.6)/2 for the 3rd line instead of null:

["2011-06-26 16:37:20",41.8, 24.4,  28.06],

I am struggling with writing the code to accomplish this task.

I would greatly appreciate any hints or assistance provided. Thank you.

//Update: I apologize for the inconvenience, but could someone please clarify why this question has received 2 downvotes? I am unsure of the reason and would appreciate feedback if I have made a mistake. Sorry for any confusion caused!

javascriptarraysaverage

Answer №1

This code demonstrates a solution using a combination of higher-order functions:

var dates = [
    ["2011-06-16 16:37:20", 23.2],
    ["2011-06-21 16:37:20", 35.6],
    ["2011-06-26 16:37:20", 41.8],
    ["2011-07-01 16:37:20", 25],
    ["2011-07-06 16:37:20", 22.8],
    ["2011-07-11 16:37:20", 36.4],
    ["2011-07-16 16:37:20", 34],
    ["2011-07-21 16:37:20", 20]];

function calculateAverage(array) {
    return (array.reduce(function(accumulator, element, index) {
        return element + accumulator;
    }, 0) / array.length).toFixed(2) * 1;
}

function manipulateData(accumulator, element, index, array) {
    element.push((accumulator.length >= 3) ? calculateAverage(accumulator) : null);
    accumulator[index % 3] = element[1];
    return accumulator;
}

dates.reduce(manipulateData, []);
dates.reverse().reduce(manipulateData, []);
dates.reverse();

Output:

[["2011-06-16 16:37:20", 23.2, null, 34.13], 
 ["2011-06-21 16:37:20", 35.6, null, 29.87], 
 ["2011-06-26 16:37:20", 41.8, null, 28.07], 
 ["2011-07-01 16:37:20", 25, 33.53, 31.07], 
 ["2011-07-06 16:37:20", 22.8, 34.13, 30.13], 
 ["2011-07-11 16:37:20", 36.4, 29.87, null], 
 ["2011-07-16 16:37:20", 34, 28.07, null], 
 ["2011-07-21 16:37:20", 20, 31.07, null]]

Answer №2

data = [
    ["2011-06-16 16:37:20",23.2],
["2011-06-21 16:37:20",35.6],
["2011-06-26 16:37:20",41.8],
["2011-07-01 16:37:20",25],
["2011-07-06 16:37:20",22.8],
["2011-07-11 16:37:20",36.4],
["2011-07-16 16:37:20",34],
["2011-07-21 16:37:20",20]
];
data.forEach(function(el,i,arr){
    var x=null,y=null;
    if(i > 2){
        x = (arr[i-3][1] + arr[i-2][1] + arr[i-1][1]) / 3;
        x = x.toPrecision(x.toString().indexOf('.') != -1 ? 2+x.toString().indexOf('.') : x.toString().length);
    }
    if(i < arr.length - 3){
        y = (arr[i+3][1] + arr[i+2][1] + arr[i+1][1]) / 3;
        y.toPrecision(y.toString().indexOf('.') != -1 ? 2+y.toString().indexOf('.') : y.toString().length);
    }
    el.push(x);
    el.push(y);
});

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