[R] lm question
Bill Venables
William.Venables at cmis.CSIRO.AU
Mon Oct 9 14:31:48 CEST 2000
> 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)
It was a typo in your data. Well, two actually. You posted
y x grp
-.9 1 a
-.8 2 a
-.7 3 a
-.7 1.5 b
-.5 2.5 b
-.3 3.5 b
-.19 2.7 c
-.11 3.7 c
-.41 4.7 c
What you meant was:
y x grp
-.9 1 a
-.8 2 a
-.7 3 a
-.7 1.5 b
-.5 2.5 b
-.3 3.5 b
-.19 2.7 c
.11 3.7 c
.41 4.7 c
Bill Venables.
--
Bill Venables, Statistician, CMIS Environmetrics Project
CSIRO Marine Labs, PO Box 120, Cleveland, Qld, AUSTRALIA. 4163
Tel: +61 7 3826 7251 Email: Bill.Venables at cmis.csiro.au
Fax: +61 7 3826 7304 http://www.cmis.csiro.au/bill.venables/
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