lmer (& siblings glmer & nlmer) are functions in the R package lme4 that fit mixed effects models (ie, models that include fixed & random effects). These models can be non-linear in the sense that the dependent variable is transformed by a non-linear function (eg, logistic or log) to accommodate ...
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10 views
lmer glht posthoc not giving pairwise comparisons
Trying to run posthoc analysis on lmer model. AOV shows significant difference between sex (three sexes) and position (four positions), both of which are factorial variables, and pl, which is ...
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63 views
Multivariate linear mixed model in R
I have run into a problem with respect to an application of linear mixed effects model using lme4 package and I wondered if I could seek your help.
This is my model in a multivariate setup where ...
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24 views
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1answer
41 views
Mixed-effects model for MZ twin data: avoiding overparametrization
I'm trying to fit a (simple) linear regression using MZ twin data. The reason why mixed-effects are used here is just to correct for correlated responses from the twins.
The current model looks like ...
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1answer
28 views
Do I need heteroscedasticity consistent Standard Errors in LMER when applying Heckman's two stage procedure?
When including an Inverse Mill's ratio to account for selection in a mixed model using LMER in R (following Heckman's [1979] two-stage procedure), do I still need to estimate robust SEs or does the ...
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1answer
65 views
“ random effects must be less than the number of observations” error in lmer package
I'm trying to implement a regression model with both fixed and random effects. The package I use is the lme4.
I want to find the relationship between the ...
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1answer
79 views
Lmer model design
My data is a series of repeated measures in time (14 measures). I am trying to model the variable HbA1c which is a blood test performed at each visit to measure the ...
2
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1answer
38 views
Quantify strength of association of two continuous variables while controlling for random effects
I have a data set from a repeated measures experimental design with different sets of stimuli. I want to know how strong the association between the continuous dependent variable and the continuous ...
2
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2answers
68 views
How do I setup a model with hierarchical structure using lmer in R?
I am trying to isolate the important predictors for my response variable "Y". I know that "TL" (which is an individual level predictor) affects "Y", and now I want to determine if adding the site ...
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1answer
43 views
how to test for overdispersion in Poisson lmer()
I have the following model:
> model1<-lmer(aph.remain~sMFS1+sAG1+sSHDI1+sbare+season+crop
+(1|landscape),family=poisson)
...and this is the summary ...
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0answers
39 views
Mixed-effect modeling with paired observations & bounded response variables
I am quite new in the field of mixed-effect modeling. For a beginner like me, I guess I combine several levels of complication in my analysis: paired observations & bounded response variables. I ...
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52 views
What does it mean to model a random effect on a main effect only when testing interaction?
I'm monitoring groups of individuals all composed of one male only and several females. I want to test if var1 is correlated with ...
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1answer
120 views
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2answers
230 views
How can I test whether a random effect is significant?
I am trying to understand when to use a random effect and when it is unnecessary. Ive been told a rule of thumb is if you have 4 or more groups/individuals which I do (15 individual moose). Some of ...
3
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1answer
108 views
Checking for outliers in a glmer (lme4 package) with 3 random factors
I have a question relating to the checking for outliers and / or influential points in my dataset using a glmer model with 3 random variables. I'm investigating the ...
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25 views
Linear model when both dependent and independent variables have unpaired replicates
I've got a set of experiments where 3 replicate measurements are done for rat cell lines and for human cell lines under different conditions using various compounds. I am trying to predict the ...
3
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0answers
58 views
Linear mixed effects model structure feedback
We are investigating the effects of a treatment (versus untreated control) on insect abundance. The study consists of 5 geographically separated study site replicates. Treatments were applied to 1 ...
2
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1answer
93 views
Linear mixed effect models: how to construct a suitable null model
Lets take as an example a repeated measures design with 10 subjects that are all reading the same letter strings and pressing a button as soon as they determine whether the string is valid English ...
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0answers
49 views
Random intercept for different groups of subjects
Is there a way to specify two different random intercept terms for two sub-groups of subjects within a single mixed model? The reason why I'm interested is that it seems that the inter-personal ...
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0answers
147 views
Using lme4 for case-controlled logistic regression?
I would like to use lmer for a conditional (or case-controlled or matched pairs) mixed effects logistic regression. However, I am not aware of any published use of ...
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55 views
When using lmer is a random intercept being estimated more than once if specified in seperate grouping factors?
I know there are a slew of lmer specification questions already floating around. Please let me know if this is a duplicate, or if it is deemed off-topic, and I'll delete it.
I am using a forward ...
2
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0answers
56 views
How close to zero should the sum of the random effects be in GLMM (with lme4)
I'm using the lme4 package in R to do some logistic mixed-effects modeling.
My understanding was that sum of each random effects should be zero.
When I make toy ...
2
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1answer
58 views
Fitting HLM models with Heavy-Tailed distribution: robust aproach to lmer?
I've been using package lmrob in R to estimate models with heavy-tailed distribution of the residuals, which I cannot correct even with transformations of the dependent variable.
I was now planing to ...
2
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0answers
131 views
How to construct GLMM model for repeated measures with binary responses with lmer
In my experiment I assigned subjects to one of the 3 treatments A, B or C. Within each treatment, a single subject was tested with two models sequentially. The test sequence was randomized. The ...
10
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178 views
In a multi-level model, what are the practical implications of estimating versus not-estimating random effect correlation parameters?
In a multi-level model, what are the practical and interpretation-related implications of estimating versus not-estimating random effect correlation parameters? The practical reason for asking this ...
3
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2answers
505 views
Variance-covariance matrix in lmer
I know that one of the advantages of mixed models is that they allow to specify variance-covariance matrix for the data (compound symmetry, autoregressive, unstructured, etc.) However, ...
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0answers
97 views
Details on specifying random parameters in 3-level HLM in R
I am used to fitting 3-level HLM with HLM software, but now I am moving to lme or lme4, from package nlme in R. Unfortunatelly, though, I am struggling a little bit with the proper ...
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1answer
201 views
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82 views
Generalized linear mixed model in R [duplicate]
Possible Duplicate:
Generalized Linear Mixed Model in R with repeated measures
I am trying to investigate how four variables (var1=continuous, var2=factor, var3=factor, var4=continuous) ...
6
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2answers
530 views
Sample size calculation for mixed models
I am wondering if there are any methods for calculating sample size in mixed models? I'm using lmer in R to fit the models (I have random slopes and intercepts).
10
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0answers
535 views
1
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176 views
Analyzing split-plot design in lme4 in R
I have the data from a split-plot design where A is my whole plot fixed factor with two levels and B is my subplot fixed factor with 2 levels and C is my random block factor. How do I analyse these ...
2
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0answers
174 views
1
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479 views
How to assign degrees of freedom for two-way ANOVA with two within-subjects factors?
I have an experiment with 44 subjects and two within-subject factors, condition (3 levels) and round (6 levels). It is fully crossed such that each person completes one of each task condition in each ...
1
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1answer
444 views
Understanding signficant interaction with non-significant main effects [duplicate]
Possible Duplicate:
How to compute significant interaction estimates when main effect is not significant?
I am an applied linguist and I am modelling responses to a vocabulary test taken by ...
3
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2answers
217 views
How to deal with repeated measurements in the same condition of a factorial experiment?
I am in Psychology and trying to explore the utility of mixed modeling for analyzing my repeated-measures data in a factorial experiment. The primary reason for using mixed models is that I would like ...
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0answers
123 views
multilevel-model, lmer()-spelling and interpretation?
I m working on a piecewise linear growth model and I need help to understand how to write my lmer() code and how to interpret the ...
4
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2answers
406 views
Contrast for hypothesis test in R (lmer)
I'm running a lmer mixed effects model with a four-level factor (levels "0","10","100","1000") as the fixed effect.
lmer(free ~ reward.f + (1|S), longdata)
I ...
3
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0answers
78 views
Testing for mediation using LMER and a Freedman and Schatzkin's method (in R)
I'm trying to analyse, whether the effect of answer correctness ($X$, binary) on confidence ratings ($Y$, continuous) in some psychological task is mediated by another rating ($M$, continuous). In ...
3
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0answers
219 views
How to interpret coefficients of a multivariate mixed model in `lme4` without overall intercept?
I'm trying to fit a multivariate (i.e., multiple response) mixed model in R. Aside from the ASReml-r and SabreR packages (which ...
5
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2answers
154 views
Hierarchical models for multiple comparisons - multiple outcomes context
I've just been (re-)reading Gelman's Why we (usually) don't have to worry about multiple comparisons. In particular the section "Multiple outcomes and other challenges" mentions using a hierarchical ...
5
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0answers
271 views
simple repeated measures syntax - lme vs. lmer
I'm trying to look for significant effects on "similarity" (of "isinpair" and controlling for time effects) using repeated measures with an in group sample. The intervention "isinpair" occurs after a ...
1
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2answers
935 views
REML vs ML stepAIC
I feel overwhelmed after attempting to dig into the literature on how to run my mixed model analysis following it up with using AIC to select the best model or models. I do not think my data is that ...
6
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1answer
1k views
Understanding the random effect in linear mixed models (lme4, R)
I am familiar with linear regression models but the random section of linear mixed models just melts my mind. I did find an excellent guide that could have helped me but the languageR package is not ...
4
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1answer
441 views
Completely different results from lmer() and lme()
I got completely different results from lmer() and lme()! Just look at the coefficients' std.errors. Completely different in both cases. Why is that and which model is correct?
...
3
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1answer
191 views
How to deal with quasi-complete separation in a logistic GLMM?
Update: Since I now know that my problem is called quasi-complete separation I updated the question to reflect this (thanks to Aaron).
I have a dataset from an experiment in which 29 human ...
15
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3answers
684 views
Interpreting three forms of a “mixed model”
There's a distinction that's tripping me up with mixed models, and I'm wondering if I could get some clarity on it. Let's assume you've got a mixed model of count data. There's a variable you know you ...
1
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1answer
97 views
Mixed effect model
I have a model:
$y=a+bx+\varepsilon_1$ for each observation (tree)
$b=c+dz+\varepsilon_2$ for each forest (group of trees)
$y$, $x$, $z$ are continuous variables. $a$, $b$, $c$, $d$ are ...
3
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2answers
354 views
Can't find p-values in the output from lmer() in the lm4 package in R
I'm a new user of mixed models and through the material I've been reading there are always probability values (p>t) or (p>z) that estimate the importance of a level of a factor in the model. However, ...
1
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2answers
632 views
Using glmer to replicate result from lmer for mulitlevel modelling in R
Having read from the internet that glmer and lmer are similar thing (correct me if I am wrong), just ...
