To comment on the following update, log in, then open the issue: http://www.openoffice.org/issues/show_bug.cgi?id=87324 Issue #|87324 Summary|regression curve with error bars incorrect Component|Chart Version|DEV300m3 Platform|All URL| OS/Version|All Status|UNCONFIRMED Status whiteboard| Keywords| Resolution| Issue type|DEFECT Priority|P3 Subcomponent|code Assigned to|kla Reported by|pmartineau
------- Additional comments from [EMAIL PROTECTED] Fri Mar 21 22:04:15 +0000 2008 ------- Thanks for the new possibility to add custom error bars, this is a fantastic improvement for the use in Sciences. However, the current implementation of the regression curve is incorrect when using error bars. Usually, error bars are interpreted as the "standard deviation" of the y. When making a regression, you should minimize Chi^2 = Sum((y-yi)^2/s^2) where s is the "standard deviation" Currently, the s parameter is not used. Whatever the values in the error column, the fit is the same. I have attached a file with simple data: X Y Error 1 1 0.1 2 1.5 1 3 3.2 O.1 With OOo, slope=1.1 intercept= -0.3 With Gnuplot, slope=1.1 intercept= -0.102985 If you use equally weighted data in Gnuplot (A constant error of 1), you get the same values that in OOo. --------------------------------------------------------------------- Please do not reply to this automatically generated notification from Issue Tracker. Please log onto the website and enter your comments. http://qa.openoffice.org/issue_handling/project_issues.html#notification --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
