From: derek <jan.kacaba_at_gmail.com>

Date: Thu, 17 Mar 2011 08:28:54 -0700 (PDT)

Date: Thu, 17 Mar 2011 08:28:54 -0700 (PDT)

Thats exactly what I would like to do. Any idea on good text? I've consulted severel texts, but no one defined R^2 as R^2 = 1 - Sum(R[i]^2) / Sum((y[i])^2-y*)) still less why to use different formulas for similar model or why should be R^2 closer to 1 when y=a*x+0 than in general model y=a*x+b.

from manual:

r.squared R^2, the â€˜fraction of variance explained by the modelâ€™,
R^2 = 1 - Sum(R[i]^2) / Sum((y[i]- y*)^2),
where y* is the mean of y[i] "if there is an intercept" and zero otherwise.

I don't need explaining what R^2 does nor how to interpret it, because I know what it means and how it is derived. I don't need to be told which model I should apply. So the answers from Thomas weren't helpful.

I don't claim it is wrong, otherwise wouldn't be employed, but I want to see the reason behind using two formulas.

Control questions:

1) Statement "if there is an intercept" means intercept including zero
intercept?

2) If I use model y = a*x+0 which formula for R^2 is used: the one with Y* or the one without?

-- View this message in context: http://r.789695.n4.nabble.com/Strange-R-squared-possible-error-tp3382818p3384844.html Sent from the R help mailing list archive at Nabble.com. ______________________________________________ R-help_at_r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.Received on Thu 17 Mar 2011 - 17:30:33 GMT

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