Dear Helpers,

I have been trying to visualise the random effects of a mixed effects  
model which was fitted with the lmer function from the lme4 package.  
Extracting the fixed and random effects works rather well with  
'coef', but when plotting this with 'by' and 'abline', something  
strange happens.

I use the following syntax (example):

fm1 <- lmer(Reaction ~ Days + (Days|Subject), sleepstudy)

sleep <- coef(fm1)$Subject
sleep$resp <- 1:18

plot(c(0,10), c(200,400), type="n")

by(sleep, resp, function(x) abline(coef=x))

This results in a basic, but acceptable, plot. However, it also  
results in quite some output at the R-Prompt. A portion of it looks  
like this:

resp: 308
NULL
-----------------------------------------------------
resp: 309
NULL
-----------------------------------------------------
resp: 310
NULL
-----------------------------------------------------
resp: 330
NULL
-----------------------------------------------------
resp: 331
NULL
-----------------------------------------------------
resp: 332
NULL


What is happening? I suspect it has something to do with my use of  
the 'by' function, but is there a way to prevent all the unwanted  
text-output?

Thanks in advance

Rense





- - -- --- ----- --------
Rense Nieuwenhuis
+31 6 481 05 683

www.rensenieuwenhuis.nl


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