[R-sig-ME] crossed random effects example
jeroenooms at gmail.com
Sun Mar 1 17:44:09 CET 2009
OK, maybe you are right. I tried the link you sent for another
example. However, also in this example, the variance of the second
random effect is estimated at zero:
pilots1 <- lmer (y ~ 1 + (1 | group.id) + (1 | scenario.id))
Groups Name Variance Std.Dev.
scenario.id (Intercept) 1.0333e-01 3.2145e-01
group.id (Intercept) 9.3719e-24 3.0614e-12
Residual 4.6738e-02 2.1619e-01
I find this very confusing. Is it also possible to have crossed random
effects that both have variance? An example would be great. Thanks
On Sun, Mar 1, 2009 at 5:24 PM, Gabor Grothendieck
<ggrothendieck at gmail.com> wrote:
> The values are the same to one decimal place and nearly the
> same to two decimal places.
> On Sun, Mar 1, 2009 at 11:12 AM, Jeroen Ooms <j.c.l.ooms at uu.nl> wrote:
>> Hello Gabor,
>> I don't understand what you mean. lmer reports a variance of treatment
>> that is practically 0:
>> Random effects:
>> Groups Name Variance Std.Dev.
>> airport (Intercept) 1.0369e-01 3.2202e-01
>> treatment (Intercept) 1.0140e-23 3.1844e-12
>> Residual 4.6991e-02 2.1677e-01
>> It seems as if lmer shows there is no variance at all for the
>> treatment effect. I think this is quite different than the 0.04
>> reported in the slide. Are you sure I did not did use the correct
>> On Sun, Mar 1, 2009 at 4:27 PM, Gabor Grothendieck
>> <ggrothendieck at gmail.com> wrote:
>>> I suspect that the slide you are referencing mislabeled the
>>> standard deviations as variances since there is reasonable
>>> correspondence between your output and the slides if that
>>> were the case.
>>> Also check out:
>>> On Sat, Feb 28, 2009 at 6:00 PM, Jeroen Ooms <j.c.l.ooms at uu.nl> wrote:
>>>> I am trying to learn about crossed random effects modeling in lme4. I
>>>> found this presentation that provides a small crossed dataset.
>>>> I would like to reproduce the variance components as reported on slide
>>>> 9 of the powerpoint. Here is my code:
>>>> y <- c(0.38,0,0.38,0,.33,1,.12,1,.25,0,.5,.12,.5,1,.12,.86,.5,.67,.33,0,.14,1,0,1,.14,0,.71,0,.29,1,.14,1,.43,0,.29,.86,.86,.86,.14,.75)
>>>> x2 <- rep(paste("airport",1:8,sep=""),5)
>>>> x1 <- rep(paste("treatment",1:5,sep=""),rep(8,5))
>>>> mydata <- data.frame(y=y,airport=x2,treatment=x1)
>>>> However, the variance components as reported by lmer are different
>>>> from the ones in the slides. What formula should I use? thank you!
>>>> R-sig-mixed-models at r-project.org mailing list
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