ng" width="700"></p>
<p>To make sense of this set of plots (actually, the same plot seen from four different angles), it will also be helpful to have the original regression results close at-hand:</p>
<div class="sourceCode"><pre class="sourceCode r"><code class="sourceCode r"><span class="kw">summary</span>(x2)</code></pre></div>
<pre><code>## 
## Call:
## lm(formula = mpg ~ hp * wt, data = mtcars)
## 
## Residuals:
##     Min      1Q  Median      3Q     Max 
## -3.0632 -1.6491 -0.7362  1.4211  4.5513 
## 