Linear regression without intercept: formula for slope To do linear regression there is good answer from TecHunter
Slope;
$$\alpha = {n\sum(xy) - \sum x \sum y \over n\sum x^2 - (\sum x)^2}$$
Offset:
$$\beta = {\sum y - \alpha \sum x \over n}$$
Trendline formula:
$$y = \alpha x + \beta $$
However, How does these formulas change when I want to force interception at origin ? I want $y=0$ when $x=0$,
so model is:
$$y = \alpha x $$ 

Since $\beta=0$, $\alpha = \frac{\sum y}{\sum x}$
