INTERCEPT(known_y's,known_x's)
INTERCEPT function calculates the point where the linear regression line intersects the y-axis.
Let us assume that the cells A1, A2, ..., A5 contain numbers 11.4, 17.3, 21.3, 25.9, and 40.1, and the cells B1, B2, ... B5 23.2, 25.8, 29.9, 33.5, and 42.7. Then
INTERCEPT(A1:A5,B1:B5) equals -20.785117212.