Click empty space to add a point, drag a point to move it, double-click a point to remove it. All four diagnostic plots below update live and share the same simulated dataset — drag a point far from the cloud and watch its leverage and Cook's distance grow. Points turn red when their Cook's distance exceeds 4/n, a common rule-of-thumb threshold for flagging unusually influential observations — the same points are flagged in the stats line and stand out on the Residuals vs. Leverage plot.