> 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.

from the current version of the lme4 package. A new version of the

package with this fixed will be uploaded shortly.

> Daniel

>

> >>> Thomas Lumley <

[hidden email]> 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

>

[hidden email] University of Washington, Seattle

>

> ______________________________________________

>

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