y moving average
values. Moving Averages are also sometimes referred to as "moving mean",
"rolling mean", "rolling average" or "running average".</p>
<p>The mean in this implementation taken from an equal number of observations
on either side of a central value. This means for an NA value at position
<code>i</code> of a time series, the observations i-1,i+1 and i+1, i+2 (assuming
a window size of k=2) are used to calculate the mean.</p>
<p>Since it can in case of long NA gaps also occur, that all values nex