[R] Help with dummy.coef

James M. Curran j.curran at auckland.ac.nz
Wed May 5 06:56:45 CEST 2010

Hi all,

I've been revising some lecture notes and I have something that used to 
work with dummy.coef and now doesn't. A search of R help doesn't reveal 
any recent discussion on this function, so I'd appreciate your thoughts. 
The (compact/relevant) code is below, and complains at the line 
rep.int(x1[[i]][1L], nl), levels = xl[[i]]) that the 'times' value is 
invalid. This seems to relate to the the polynomial terms, but I'm not 
sure how to take it further than that.

battery.df = data.frame(
            voltage = c(130,155,74,180,34,40,80,75,20,70,82,
           material = factor(rep(1:3,rep(12,3))),
             temp = rep(rep(c(50,65,80),rep(4,3)),3))

battery.df = data.frame(voltage, material, temp)
battery.fit=lm(voltage~material*(temp+I(temp^2)),data = battery.df)


Error in rep.int(xl[[i]][1L], nl) : invalid 'times' value


James M. Curran, Ph.D.
Associate Professor
Director Bioinformatics Institute
Department of Statistics
Faculty of Science
Private Bag 92019
New Zealand

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