title: Predict future values with a moving weighted average
body: <p>I would like to use an exponential moving average (or weighted moving average) to impute the values for all NaNs. So far I've found how to add new columns but not how to add the data into the existing rows. Is there a way to fill out the data using the previous 3 values?</p>
  <p><a href="https://i.stack.imgur.com/D1DfD.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/D1DfD.png" alt="enter image description here" /></a></p>