From: Ajay Narottam Shah <ajayshah_at_mayin.org>

Date: Wed 15 Jun 2005 - 12:36:34 EST

Date: Wed 15 Jun 2005 - 12:36:34 EST

> > I have a program which is doing a few thousand runs of lm(). Suppose

*> > it is a simple model
**> > y = a + bx1 + cx2 + e
**> >
**> > I have the R object "d" where
**> > d <- summary(lm(y ~ x1 + x2))
**> >
**> > I would like to obtain Var(x2) out of "d". How might I do it?
**> >
**> > I can, of course, always do sd(x2). But it would be much more
**> > convenient if I could snoop around the contents of summary.lm and
**> > extract Var() out of it. I couldn't readily see how. Would you know
**> > what would click?
**>
**> Is the question how to get the variance of a column of the
**> model matrix for a model that is the sum of terms given only
**> summary output and the column name but not the name of the
**> data frame? If that is it then try this:
**>
**> d <- summary(lm(Sepal.Length ~ Sepal.Width, iris)) # test data
**> var(model.matrix(eval(d$call))[,"Sepal.Width"])
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Yes, this is indeed exactly what I was looking for :-) Thanks,

The eval() pays the full cost of running d$call?

-ans.

-- Ajay Shah Consultant ajayshah@mayin.org Department of Economic Affairs http://www.mayin.org/ajayshah Ministry of Finance, New Delhi ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.htmlReceived on Wed Jun 15 13:31:36 2005

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