To comment on the following update, log in, then open the issue: http://www.openoffice.org/issues/show_bug.cgi?id=78250 Issue #|78250 Summary|BROKEN Functions Component|Spreadsheet Version|OOo 2.2 Platform|All URL| OS/Version|All Status|UNCONFIRMED Status whiteboard| Keywords| Resolution| Issue type|DEFECT Priority|P2 Subcomponent|code Assigned to|spreadsheet Reported by|discoleo
------- Additional comments from [EMAIL PROTECTED] Fri Jun 8 19:25:55 +0000 2007 ------- UNSTABLE COMPUTER ALGORITHMS USED A. ERROR Various functions are affected, including: CORREL()-series RSQ(), and STEYX() As already pointed out on the dev-calc mailing list and the OASIS mailing list, various functions use an unstable algorithm: algorithms based on [n*sum(x[i]2) - sum(x[i])2] are inherently unstable I will attach a test-case, where: CORREL() computes an impossible value of -1.69 RSQ() computes an impossible value of 2.29, and STEYX() gives a '#VALUE!' ERROR Please note, that in these instances, through the mathematically impossible values, we are hinted that the calculation went very wrong. However, even *PLAUSIBLE* values can be completely erroneous!!! [And one has NOT the feedback that something went wrong!] Therefore I put a P2 priority. A. SOLUTION Use stable algorithms (as discussed on the lists). Classically, a two-pass algorithm will be stable, BUT there would be a time penalty (especially for RSQ(), where we need 3 passes!). Implement a fast version of the functions, like RSQFAST(), CORRELFAST(), ..., that use a fast and reliable (therefore more stable) *one-pass* algorithm. C. TEST CASE ATTACHED --------------------------------------------------------------------- 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]
