MatPed,
yes you are right; I would plot the standard regression straight line which of course needs 2 values ( as per my picture above ).
My final target would be also to plot the regression channels of the series.
If you could provide also the r-squared value like in the picture below, would be great.
https://drive.google.com/open?id=0B7OAmRgfpHP-YkVycXJIeXNRQlECiao