[R] How to predict the mean and variance of the dependent variable after regression

Joshua Wiley jwiley.psych at gmail.com
Mon Jun 21 20:34:28 CEST 2010


If you just want the mean and variance of log(y) try:


if there is missing data, you can add na.rm=TRUE to both of those.  If
you want the mean and variance of the predicted ys



?predict.lm #the specific method being used for predict() with model
objects of class lm



On Mon, Jun 21, 2010 at 11:24 AM, Yi <liuyi.feier at gmail.com> wrote:
> Hi, folks,
> As seen in the following codes:
> x1=rlnorm(10)
> x2=rlnorm(10,mean=2)
> y=rlnorm(10,mean=10)### Fake dataset
> linmod=lm(log(y)~log(x1)+log(x2))
> After the regression, I would like to know the mean of y. Since log(y) is
> normal and y is lognormal, I need to know the mean and variance of log(y)
> first.  I tried mean (y) and mean(linmod), but either one is what I want.
> Any tips?
> Thanks in advance!
>        [[alternative HTML version deleted]]
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Joshua Wiley
Ph.D. Student
Health Psychology
University of California, Los Angeles

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