## 5.4 Inertia of a cloud of points

We measure the inertia of a cloud with respect to its of gravity by:

$I = \sum_{i=1}^{n} p_i \hspace{1mm} d^2(i,G)$

The inertia is a measure of spread; to be more precise, it is a measure of weighted spread of the points.

The statistical notion associated to the inertia is the variance (i.e. spread around the mean).