[R] help with coef

[Gabor Grothendieck]

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
>
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>
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