Submitted by Morten Welinder

Link to original bug (#779177)

Description

Created attachment 346633 Sample file

1-Jan-2001 1 1-Jan-2002 3 1-Jan-2003 2 1-Jan-2004 5 1-Jan-2005 4 1-Jan-2006 7 1-Jan-2007 6 1-Jan-2008 9 1-Jan-2009 8 1-Jan-2010 10

Graph that data and add a linear regression and an equation to go with that. I see "0.00260507x-94.887".

That is, I'm sure, a correct equation, but in contains in it raw information about the date system we use.

0.002507 makes sense: it is increment per day.

-94.889 does not: it is the predicted Y value for 1-Jan-1900. (Bearing in mind that we have a hole in the date numbering where 1900-02-29 would have been and that all date is after that hole, the right date is probably 1899-Dec-31.)

I think we would be better off presenting the result as

0.00260507(x-"1-Jan-2000")+1.2

Attachment 346633, "Sample file":
date-axis-regression.gnumeric

Version: GIT