Trailing HR / moving average HR - and a question on eliminating HR spikes

[DonTomGot]

To smoothen HR and minimize fluctuations I have previously used (Ambit2) trailing HR - but it seems it now needs to be calculated. As I had some problems in succeeding with this pretty simple task I thought someone else might benefit from my findings/hypothesis.

Initially I tried this, to achieve a trailing (5s) heartrate:

function evaluate(input, output) {

HRacc5.shift(); //shifts the array one step left

HRacc5[4] = input.HRCurrent; //adds current heart rate to index 4 in array

var calculateAverage = function(arr) {
    var sum = 0;
    for (var i = 0; i < arr.length; i++) {
        sum += arr[i];
    }
    return sum / arr.length;
}

var HRavg5 = calculateAverage(HRacc5);

output.RecalcAvgHR = 60 * HRavg5;

Which worked well in the simulator. But IRL it did not work at all. The watch froze after a couple of minutes in all workouts and it became quite frustrating since troubleshooting on watch seemed advanced - and I am not advanced.

As the watch seemed to freeze at very random points - sometimes 20 mins into a workout - I came to the conclusion that perhaps the input causes friction, as it works in the simulator? the hypothesis is now that unregistered heartbeat returns ‘undefined’ so next attempt was the inclusion of:

HRacc5 = HRacc5.filter(Number);

Supposedly filtering out everything that is not recognized as numbers.

Now the app worked!

(writing this primarily to avoid repeating the same frustrating workouts again, and potentially help others with similar ideas)

Second topic: Sometimes (often when tired/poor sleep quality/hung over) I get heart rate spikes that I would like to eliminate. I would imagine that they can be identified as rapid elevations in heart rate where also the trailing heart rate can be a good baseline. But how could an algorithm be designed to eliminate these spikes with minimum disturbance to the trailing HR? All input most welcome!