[R] multiple GLMs with lmList in lme4

[Douglas Bates]

On 1/17/06, Daniel Farewell <farewelld at cardiff.ac.uk> wrote:
> Many thanks! That'll work great. It's always good to discover a new, general, function like by().
>
> I would still be interested to know how the family argument to lmList() should be used.

As you have discovered the family argument has no effect in lmList()
from the current version of the lme4 package.   A new version of the
package with this fixed will be uploaded shortly.

> Daniel
>
> >>> Thomas Lumley <tlumley at u.washington.edu> 01/17/06 3:15 pm >>>
> On Tue, 17 Jan 2006, Daniel Farewell wrote:
>
> > I'd like to fit a GLM to each of a number of subsets of some data. The
> > `family' argument to `lmList' (in lme4) has given me cause for optimism,
> > but so far I've only been able to achieve linear model fits. For example
> >
> >> df <- data.frame(gp = gp.temp <- factor(rep(1:3, each = 100)),
> > x = x.temp <- rnorm(300),
> > y = rpois(300, exp((-1:1)[gp.temp] + x.temp)))
>
> Unless you are particularly attached to lmList() you might try by():
>
> by(df,df$gp,function(subset) glm(y~x,family=poisson,data=subset))
>
>         -thomas
>
>
> >
> > Then a call to `glm' on the group 1 subset gives
> >
> >> glm(y ~ x, family = poisson, data = df, subset = gp == 1)
> >
> > Call:  glm(formula = y ~ x, family = poisson, data = df, subset = gp == 1)
> >
> > Coefficients:
> > (Intercept)            x
> >    -1.0143       0.9726
> >
> > Degrees of Freedom: 99 Total (i.e. Null);  98 Residual
> > Null Deviance:      138.5
> > Residual Deviance: 82.76        AIC: 178.5
> >
> > (the right answer) but `lmList' gives
> >
> >> show(lmList(y ~ x | gp, family = poisson, data = df))
> > Call: lmList(formula = y ~ x | gp, data = df, family = poisson)
> > Coefficients:
> >  (Intercept)         x
> > 1   0.5560377 0.6362124
> > 2   1.8431794 1.8541193
> > 3   4.5773106 4.7871929
> >
> > Degrees of freedom: 300 total; 294 residual
> > Residual standard error: 2.655714
> >
> > which come from linear model fits, e.g.
> >
> >> lm(y ~ x, data = df, subset = gp == 1)
> >
> > Call:
> > lm(formula = y ~ x, data = df, subset = gp == 1)
> >
> > Coefficients:
> > (Intercept)            x
> >     0.5560       0.6362
> >
> > Any suggestions as to why lmList matches the linear fits rather than the GLM fits would be greatly appreciated. I'm using R2.2.1 with lme version 0.98-1 in Windows XP.
> >
> > Daniel Farewell
> > Cardiff University
> >
> > ______________________________________________
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> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
> >
>
> Thomas Lumley                   Assoc. Professor, Biostatistics
> tlumley at u.washington.edu        University of Washington, Seattle
>
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