[R] Using termplot() with transformations of x

Peter Dunn pdunn2 at usc.edu.au
Fri Aug 27 01:10:13 CEST 2010

Hi all

I was playing with termplot(), and came across what appears to be an inconsistency.

It would appreciate if someone could enlighten me:

> # First, generate some data:
> y <- rnorm(100)
> x <- runif(length(y),1,2)

> # Now find the log of x:
> logx <- log(x)
> # Now fit two models that are exactly the same, but specified differently:
> m1 <- lm(y~log(x)) # Using log in the call
> m2 <- lm(y~logx) # Using the variable logx
> # The two termplots() are different:
> par(mfrow=c(1,2))
> termplot(m1)
> termplot(m2)

I see two models that are identical, but produce different termplot()s.  In both cases, the independent variable is log(x), but is just specified differently.

If this is intended, what is the logic?  Or am I missing something?



> sessionInfo()
R version 2.11.1 (2010-05-31) 

[1] en_AU.UTF-8/en_AU.UTF-8/C/C/en_AU.UTF-8/en_AU.UTF-8

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

Peter Dunn: Biostatistician (Room T4.12)
School of Health and Sport Science
Faculty of Science, Health and Education  ML-34
University of the Sunshine Coast, Locked Bag 4
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Tel: +61 7 5456 5085
Fax: +61 7 5430 2896
Email: pdunn2 at usc.edu.au

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