lude hat-values (leverages), generalized Cook's distance and
generalized squared 'studentized' residuals.  Several types of plots to detect
influential observations are provided.</p>
<p>In addition, the functions provide diagnostics for deletion of subsets of observations
of size <code>m&gt;1</code>. This case is theoretically interesting because sometimes pairs (<code>m=2</code>)
of influential observations can mask each other, sometimes they can have joint influence
far exceeding their individual effects,