[R] Different random intercepts but same random slope for groups

[Bert Gunter]

Thierry:

I don't think so. It looks to me like her syntax/understanding is confused.
I think the call should be:

mod2 <- lmer(result  ~ group*time+(group + time|lot), na.action=na.omit,
data=alldata)

Her request for "the same random slope for each group" -- I assume it's for
time -- means to me that the time slope will vary "randomly" by lot only,
the slope would be the same for all groups within the lot.

Of course, I may be wrong also. If so, I suggest that she follow the
posting guide and post at least head(alldata) using dput() to enable folks
to understand the structure of her data. And only on r-sig-mixed-models --
crossposting is frowned upon here and the mixed models list is the best bet
for this sort of question anyway.

As always, corrections and criticism welcome.

Cheers,
Bert

Bert Gunter

"Data is not information. Information is not knowledge. And knowledge is
certainly not wisdom."
   -- Clifford Stoll

On Tue, Jun 9, 2015 at 1:49 PM, Thierry Onkelinx <thierry.onkelinx at inbo.be>
wrote:

> Your model is too complex for the data. This gives you two options: a)
> simplify the model and b) get more data.
>
> Best regards,
>
> ir. Thierry Onkelinx
> Instituut voor natuur- en bosonderzoek / Research Institute for Nature and
> Forest
> team Biometrie & Kwaliteitszorg / team Biometrics & Quality Assurance
> Kliniekstraat 25
> 1070 Anderlecht
> Belgium
>
> To call in the statistician after the experiment is done may be no more
> than asking him to perform a post-mortem examination: he may be able to say
> what the experiment died of. ~ Sir Ronald Aylmer Fisher
> The plural of anecdote is not data. ~ Roger Brinner
> The combination of some data and an aching desire for an answer does not
> ensure that a reasonable answer can be extracted from a given body of data.
> ~ John Tukey
>
> 2015-06-09 21:57 GMT+02:00 li li <hannah.hlx at gmail.com>:
>
> > Hi all,
> >   I'd like to fit a random intercept and random slope model. In my
> > data, there are three groups. I want to have different random
> > intercept for each group but the same random slope effect for all
> > three groups. I used the following R command.
> > However, there seems to be some problem. Any suggestions?
> >
> >
> >
> > mod2 <- lmer(result  ~ group*time+(0+group1+ group2 +
> > group3+time|lot), na.action=na.omit, data=alldata)
> >
> > > summary(mod2)
> > Model is not identifiable...
> > summary from lme4 is returned
> > some computational error has occurred in lmerTest
> > Linear mixed model fit by REML ['merModLmerTest']
> > Formula: result ~ group * time + (0 + group1 + group2 + group3 + time |
> >     lot)
> >    Data: alldata
> >
> > REML criterion at convergence: 807.9
> >
> > Scaled residuals:
> >     Min      1Q  Median      3Q     Max
> > -3.0112 -0.3364  0.0425  0.2903  3.2017
> >
> > Random effects:
> >  Groups   Name     Variance Std.Dev. Corr
> >  lot      group1   0.00000 0.000
> >           group2   86.20156 9.284      NaN
> >           group3 55.91479 7.478      NaN  0.06
> >           time      0.02855 0.169      NaN -0.99  0.10
> >  Residual          39.91968 6.318
> > Number of obs: 119, groups:  lot, 15
> >
> > Fixed effects:
> >                             Estimate Std. Error t value
> > (Intercept)                 100.1566     2.5108   39.89
> > group  group2        -2.9707     3.7490   -0.79
> > group  group3           -0.0717     2.8144   -0.03
> > time                         -0.1346     0.1780   -0.76
> > group  group2 :time   0.1450     0.2939    0.49
> > group  group3:time        0.1663     0.2152    0.77
> >
> > Warning messages:
> > 1: In checkConv(attr(opt, "derivs"), opt$par, ctrl = control$checkConv,
> :
> >   Model failed to converge with max|grad| = 0.147314 (tol = 0.002,
> > component 2)
> > 2: In checkConv(attr(opt, "derivs"), opt$par, ctrl = control$checkConv,
> :
> >   Model failed to converge: degenerate  Hessian with 2 negative
> eigenvalues
> >
> > ______________________________________________
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> > PLEASE do read the posting guide
> > http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
> >
>
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>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
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> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

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