[R] help with coef

[Gabor Grothendieck]

On 10/21/06, tom soyer <tom.soyer at gmail.com> wrote:
> Gabor,
>
> Thanks for the code example, but it seems that BOD is not needed. I still

demand and Time are columns of BOD so if you omit it then it won't know
where they are.

> don't understand what is going on with the data structure returned by
> coef(). The strangness is illustrated by the following example:

coef returns a named vector.  as.vector returns an unnamed vector.

>
> > a=coef(lm(y~miles))
> > is.vector(a)
> [1] TRUE
> > a[2]
>   miles
> -7.2875
> > a=as.vector(a)
> > is.vector(a)
> [1] TRUE
> > a[2]
> [1] -7.2875
>
> As you can see, although coef() returns a vector already, only after
> as.vector(a) is used, did a[2] include the slope without the name of the
> slope. Why is that, and what happened to the name of the slope (names(a)
> returns NULL)?
>
> Tom
>
> On 10/20/06, Gabor Grothendieck <ggrothendieck at gmail.com> wrote:
> > Using the builtin BOD data frame:
> >
> > as.vector(coef(lm(demand ~ Time, BOD)))[2]
> >
> >
> > On 10/21/06, tom soyer < tom.soyer at gmail.com> wrote:
> > > Hi,
> > >
> > > I am trying to get R to return just the slope of a linear regression
> line,
> > > but it seems that R has to return both the slope and the name of the
> slope.
> > > For example,
> > >
> > > > a=coef(lm(y~miles))
> > > > a
> > > (Intercept)       miles
> > >   360.3778     -7.2875
> > > > names(a)
> > > [1] "(Intercept)" "miles"
> > > > a[1]
> > > (Intercept)
> > >   360.3778
> > > > a[2]
> > >  miles
> > > -7.2875
> > >
> > > I don't understand the data structure that's returned from coef().
> names(a)
> > > seems to suggest that coef() returns two columns of data, column one is
> the
> > > Intercept, and column two miles. But R keeps telling me that the return
> > > value from coef() has only one dimension, i.e., a[,2] doesn't work, but
> a[2]
> > > works. However, a[2] contains more than the slope, it also has the name
> of
> > > the slope. Does anyone know how to access just the slope without its
> name?
> > >
> > > Thanks,
> > >
> > > Tom
> > >
> > >        [[alternative HTML version deleted]]
> > >
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>
>