Keys: press [ or ] to pick a handle or the whole line. Press ↑ or ↓ to move it one step. Hold Shift with an arrow key to move it five steps.
Residual vector
The drawn line is the least squares line. No other line has a shorter residual vector.
R
Line comparison
A row loads its line.
Squared residuals
The side of each square is one residual. The area of the square is that residual squared. The total area of the squares is ‖r̅‖². The least squares line has the smallest total area of any line.