[R] lm question

[Bill Simpson]

Thanks very much Peter, Martyn, and Brian for the help.

> > lm(y~x:(grp-1)+1)
> 
> Call:
> lm(formula = y ~ x:(grp - 1) + 1)
> 
> Coefficients:
> (Intercept)       x.grpa       x.grpb       x.grpc  
>    -0.80977      0.01847      0.13124      0.14259  
It seems to me that there is something seriously wrong here since for the
data I posted (I just re-checked it),
intercept=-1, slope a=.1, slope b=.2, and slope c = .3
(These fit the data exactly)

This leaves aside the comments of Martyn and Brian.

Bill

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