freedom,
 usually abbreviated MSE.
 <p>
 If there are fewer than <strong>three</strong> data pairs in the model,
 or if there is no variation in <code>x</code>, this returns
 <code>Double.NaN</code>.</p></div>
<dl><dt><span class="strong">Returns:</span></dt><dd>sum of squared deviations of y values</dd></dl>
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<h4>getR</h4>
<pre>public&nbsp;double&nbsp;getR()</pre>
<div class="block">Returns <a href="http://mathworld.