[R-sig-ME] call for help

[Carlos Familia]

Hi,

I normally use the following code to check for assumptions:

par(mfrow=c(2,2))

plot(fitted(mdl),residuals(mdl), pch = '.')
abline(lm(y ~ x, data = data.frame(y = residuals(mdl), x = fitted(mdl))), col = 'red')
abline(a=0, b=0, lty=3)

plot(fitted(mdl), amps.long$mic, pch = '.', ylab = 'observed')
abline(lm(y ~ x, data = data.frame(y = amps.long$mic, x = fitted(mdl))), col = 'red')
abline(a = 0, b = 1, lty=3)

qqnorm(residuals(mdl))
qqline(residuals(mdl))

hist(residuals(mdl),breaks = 50, probability = T)
lines(density(residuals(mdl)), col = "red")
par(mfrow=c(1,1))

There are other ways to do it, and you should know what are the assumptions, for that I suggest for you to take a loot at Douglas Bates book.

Best regards,
Carlos Família

Carlos Familia, MPharm, PharmD
ISCSEM Assistant Lecturer
ISCSEM Laboratory of Molecular Pathology Researcher
ISCSEM Erasmus Mundus Master in Forensic Sciences Vice-coordinator
Tel. +351 212946700 (Main) / +351 212946769 (Lab)
e-mail: carlosfamilia at gmail.com / carlosfamilia at egasmoniz.edu.pt

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> On 10 Oct 2016, at 00:37, 罗波 <luob041 at nenu.edu.cn> wrote:
> 
> Dear Experts,
> 
> 
> Nice to meet you! I am a Ph.D. student from Northeast Normal University in China. My research field is behavioral ecology. Thanks for your contribution to develop the package 'lme4'.
> That's really nice and valuable!
> 
> 
> Recently, I would like to fit the linear mixed model using the experimental data. Following the examples listed  in the  guide, I know how to achieve it using your package. Yet, I wonder if my data
> satisfy the model assumption. I have two major confusions (see followings). Would you please give me some help?
> 
> 
> Does it require normality of model residuals, homoscedasticity, absenceof collinearity between predictors or perhaps others?
> 
> 
> If so, how can I check whether  my data satisfy the assumption? Would you please provide some advice or R code?
> 
> 
> Really need your help! Thanks very much!
> 
> 
> Best,
> Bo
> 
> 
> 
> 
> 
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> 
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