Extrapolate best-fit line

Hello,

This is a section of one of my plots. I am estimating the slope of the "crosses data", i.e. the star is not included in that estimation (I am just using it as a reference value). I want to show that my best fit of the crosses also passes through that star. How can I extrapolate this without having to include the star in my estimate? Thanks

Answer 1

[Torsten]

If you have the coefficients c(1) and c(2) of the fit line l(x)=c(1)+c(2)*x, just evaluate the equation at the x-coordinate of the star point and compare with the y-coordinate of the star point.