Hello. precompiled R-2.15.0, svn58871, macosx 10.7.4.
I have discovered that defining column names of a dataframe can alter the
behaviour of lm():
d <- c(4,7,6,4)
x <- data.frame(cbind(0:3,5:2))
coef(lm(d~ -1 + (.)^2,data=x))
X1 X2 X1:X2
-1.77 0.83 1.25
R>
R>
OK, so far so good. But change the column names of 'x' and the behaviour
changes:
colnames(x) <- c("d","nd") # 'd' == 'death' and 'nd' == 'no death'
coef(lm(d~ -1 + (.)^2,data=x))
nd
0.2962963
I am not sure if this is consistent with the special meaning of '.'
described under ?formula.
Is this the intended behaviour?
--
Robin Hankin
Uncertainty Analyst
hankin.ro...@gmail.com
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