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<h2><b>smth9</b></h2><p> 

<code>smth9(<i>expr</i>)</code><p>

Performs a 9 point smoothing to the gridded result of the
<code><i>expr</i></code>.<p> 

<h3>Usage Notes</h3><p>

<ol>
<li>The result at each grid point is a weighted average of the grid point
plus the 8 surrounding points. The center point receives a wieght of 1.0,
the points at each side and above and below receive a weight of 0.5, and
corner points receive a weight of 0.3.<p>

<li>All 9 points are multiplied by their weights and summed, then divided
by the total weight to obtain the smoothed value. Any missing data points
are not included in the sum; points beyond the grid boundary are
considered to be missing. Thus the final result may be the result of an
averaging with less than 9 points. <p>

<li>If the gridded data is 1-Dimensional, the result is a 3 point
smoothing. 
</ol>

<H3>Examples</H3><P>