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A consultation about DF of the result of lmer

2 messages · 何如梦, Ben Bolker

何如梦
# 
Dear, 
I am a graduated student who's topic is  ecology. Recently, I am studying how to establish a liner mixed model to exclude the error caused by the difference of site by using lme4 in R. I found  when I calculated p value by using the function of "Anova" of car package the Df is 1. But in fact the data set has 6 levels. Then I also operate according to the code of reference PDF of lme4 in P52(lmer) without any change. When run "anova(fm1, fm2)" I found the Df of fm1 also is 1. As I see if the Df is wrong the p value would be wrong either. I want to know how to correct my wrong. I will very appreciate your reply.


Best regards,
Rumeng He
1 day later
Ben Bolker
# 
It's very hard to say without more information (try e.g. here
<https://stackoverflow.com/questions/5963269/how-to-make-a-great-r-reproducible-example>
or look at other posts in the list archive
<https://stat.ethz.ch/pipermail/r-sig-mixed-models/>

  A first guess is that you have a fixed-effect predictor that's
supposed to be a factor with 6 levels, but is actually being interpreted
as a numeric variable.  If that's the case, then either changing it
within the data set

  mydata$pred1 <- factor(mydata$pred1)

or doing it on the fly in your  model

  lmer(response ~ factor(pred1) + ...)

should fix the problem.
On 2019-05-05 9:11 p.m., ??? wrote: