Hi Saiwing,
If all you are asking is how to rename a factor vector, the easiest way
would be to use:
levels(Loblolly$Seed) <- c( a vector of level names you would like to use
for the factor - separated by commas)
If you are asking how to make your output look better, I am not sure I have
an idea (except for using "summary(fit)" - but I guess that is not what you
mean)
Best,
Tal
On Sat, Mar 21, 2009 at 11:02 PM, Saiwing Yeung <saiw...@berkeley.edu>wrote:
> Hi all,
>
> I have a pretty basic question about categorical variables but I can't seem
> to be able to find answer so I am hoping someone here can help. I found that
> if the factor names are all in numbers, fitting the model in lm would return
> labels that are not very recognizable.
>
> # Example: let's just assume that we want to fit this model
> fit <- lm(height ~ age + Seed, data=Loblolly)
>
> # See the category names are all mangled up here
> fit
>
>
> Call:
> lm(formula = height ~ age + Seed, data = Loblolly)
>
> Coefficients:
> (Intercept) age Seed.L Seed.Q Seed.C
> Seed^4
> -1.31240 2.59052 4.86941 0.87307 0.37894 -0.46853
> Seed^5 Seed^6 Seed^7 Seed^8 Seed^9 Seed^10
> 0.55237 0.39659 -0.06507 0.35074 -0.83442 0.42085
> Seed^11 Seed^12 Seed^13
> 0.53906 -0.29803 -0.77254
>
>
>
> One possible solution I found is to rename the categorical variables
>
> seed.str <- paste("S", Loblolly$Seed, sep="")
> seed.str <- factor(seed.str)
> fit <- lm(height ~ age + seed.str, data=Loblolly)
> fit
>
>
>
> Call:
> lm(formula = height ~ age + seed.str, data = Loblolly)
>
> Coefficients:
> (Intercept) age seed.strS303 seed.strS305 seed.strS307
> -0.4301 2.5905 0.8600 1.8683 -1.9183
> seed.strS309 seed.strS311 seed.strS315 seed.strS319 seed.strS321
> 0.5350 -1.5933 -0.8867 -0.3650 -2.0350
> seed.strS323 seed.strS325 seed.strS327 seed.strS329 seed.strS331
> 0.3067 -1.3233 -2.6400 -2.9333 -2.2267
>
>
> Now it is actually possible to see which one is which, but is kind of lame.
> Can someone point me to a more elegant solution? Thank you so much.
>
> Saiwing Yeung
>
> ______________________________________________
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> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
--
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