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------- Additional comments from [EMAIL PROTECTED] Tue Jul 11 13:00:39 -0700 2006 ------- "As scientifically working student" you should question if this a valid thing to do. If a physical relationship is known to go through zero and your data does not, you should analyse why that is and write an appropriate conclusion not falsify your results by arbitarily forcing a false fit. One common reason for this effect (apart from experimental error) is that least squares fit assumes that the y residuals are far greater than the x residuals. ie. x is a controlled variable with negligable error s.t. rx/ry -> 0 If this is not the case, the derivation of the least squares line fit is NOT mathematically valid. I have seen examples if dispersed data where the least squares fit was "visibly" wrong by a significant degree. The data did not fit the above requirement and the fit was garbage. Most people are quite ignorant of this important limitation in using linear regression. Least squares can also be strongly influenced by an erroneous data point (a flyer). One further cause is that most implementations of least squares minimise the squares of the y residuals not the perpendiculars to the fitted line. I see little use of this "feature" as suggested. If a user wants to add a fictive slope to his data he can simply add a line close to the lin. regression fit then remove the true line. Adding this as a function will simply mislead non-technical users into thinking that this is an alternative VALID regression fit. It is not. That would seem undersirable. --------------------------------------------------------------------- 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]
