[R-sig-eco] ANCOVA with random effects for slope and intercept
Mollie Brooks
mbrooks at ufl.edu
Tue Nov 4 13:41:23 CET 2014
Hi Dr. Houk,
You say you get the same result from the lmer model as a linear model.
Can you show us the summary of both models so that we might help you interpret it?
Thanks,
Mollie
------------------------
Mollie Brooks, PhD
Postdoctoral Researcher, Population Ecology Research Group
Institute of Evolutionary Biology & Environmental Studies, University of Zürich
http://www.popecol.org/team/mollie-brooks/
> On 4Nov 2014, at 13:30, peterhouk1 . <peterhouk at gmail.com> wrote:
>
> Greetings -
>
> Looking for advice and insight into ANCOVA models that allow for random
> slope and intercept effects. I have been using lme and lmer, but I can't
> seem to figure out where I've gone wrong. I have a grouping factor,
> predictor, and response. The response~predictor relationship should be
> nested within grouping factor, with a desire to allow for random effects of
> the slope and y-intercept. Data and my code are found below, greatly
> appreciate insight.
>
> I get the same response from both approaches:
>
> Mlme1<-lme(response~predictor,
> random = list(group_factor = ~1 | predictor), data=mydata)
>
> Second approach
>
> Mlmer1<-lmer(response~predictor + (1 + predictor|group_factor), data=mydata)
>
> Taking both approaches, I get the same results as a simple linear model
> that does not account for nesting within the group factor.
>
> mydata
>
> group_factor predictor response 1 13.75584744 -0.257259794 1 3.059971584
> 0.703113472 1 14.00447296 -0.260892287 1 6.705509001 -0.33269593 1
> 6.592728067 0.053814446 1 9.211047122 -0.002776485 2 12.50497696
> 0.22727311 2 7.059077939 0.18586719 2 6.617249805 -0.022951714 2
> 1.559557719 0.833397702 2 12.1962121 -0.57159955 2 11.29647955
> -0.963754818 2 15.54334219 0.489700014 3 8.93626518 -0.421471799 3
> 1.681675438 0.383260174 3 13.43826892 -0.330882653 3 10.8971089 0.47675377
> 3 7.600869443 -0.227033926 3 15.004137 0.104257183 4 12.61327214
> 0.131460302 4 3.788474342 0.079758467 4 14.37299098 0.294254076 4
> 3.564225024 -0.006581881 4 13.63301652 -0.498890965 5 4.36777119
> 0.90215334 5 5.150130473 0.098069832 5 7.875920526 0.468166528 5
> 13.91344257 -0.291551635 5 10.1061938 -0.35162982 5 13.32810817
> 0.133439251 5 15.64845612 -0.439418202 5 1.857959976 -0.468857357 5
> 11.31495202 -0.050371938 6 7.851162116 0.126588358 6 5.285251391
> 0.212699384 6 15.82353883 -0.202005195 6 11.90209318 0.34412633 6
> 5.547563146 -0.446233668 6 5.645270991 -0.303913602 6 8.668938138
> 0.268738394 7 15.66063395 -0.194882955 7 11.11830972 0.196309336 7
> 3.174056086 0.188199892 7 12.39006821 0.222261643 7 3.034014836
> 0.039201594 7 13.13551529 -0.451089511 8 9.990570964 -0.128411654 8
> 2.382739273 0.145897042 8 4.870002628 0.875223363 8 5.99541207 0.155610264
> 8 16.56247927 -0.461697164 8 14.58286908 -0.514244888 8 12.72137648
> -0.072376963 9 7.436676598 -0.306969441 9 5.196390457 -0.222063871 9
> 7.213670545 -0.411344562 9 9.243636562 0.095582355 9 7.029863529
> 0.31586562 9 6.074354561 0.459471079 9 8.282168564 0.632851023 9
> 13.85105359 -0.298326302 9 5.972744894 -0.180974348 9 14.09541111
> -0.084091553 10 5.304552826 0.265618935 10 4.089248332 0.270559629 10
> 7.482418571 0.049764287 10 16.44388769 0.008163962 10 13.78009474
> -0.594106812 11 10.34249094 -0.206619307 11 4.491492572 -0.207263365 11
> 7.350436798 0.083703414 11 8.38636562 0.330179258
>
> --
>
> Peter Houk, PhD
> Assistant Professor
> University of Guam Marine Laboratory
> http://www.guammarinelab.com/peterhouk.html
> www.pacmares.com
> www.micronesianfishing.com
>
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