View source for Template:NA Handling Table

In calculations, NA values in the inputs yield NAs as outputs by default.  Optionally, you can fill the inputs with their neighboring values before they are evaluated. In particular:
<ul>
<li>Fill forward</li>
<li>Fill backward</li>
<li>Fill forward, then backward</li>
<li>Fill backward, then forward</li>
<li>For example:  <i>Fill Forward, then Backward</i> of <i>NA, 2, NA, 4, NA</i> yields<i>2, 2, 2, 4, 4</i></li>
</ul>