How to fit two random effects separately in lme?
nlme, r, random
Solution
I think it is possible to include two random effects seperately (one for speaker and one for time) using `lme()` by the following code:
x4 <- lme (DV ~ IV1 + IV2 + IV1*IV2, data=a.frame, random=~ speaker + item -1 | id),
with `id` a higher level variable in which both `speaker` and `item` are nested. If you don't have such a variable, you could introduce it as a new variable with value 1 for all observations.
Problem
I'm doing Linear mixed-effects model fit by REML in nlme package. And these are codes that work for me: ``` # Linear mixed-effects model fit by REML (intercept and not slope) x <- lme (DV ~ IV1 + IV2 + IV1*IV2, data=a.frame, random=~1|speaker) summary(x) # Linear mixed-effects model fit by REML (slope and no intercept) x1 <- lme (DV ~ IV1 + IV2 + IV1*IV2, data=a.frame, random=~IV3-1|speaker) summary(x1) # Linear mixed-effects model fit by REML (slope and intercept) x2 <- lme (DV ~ IV1 + IV2 + IV1*IV2, data=a.frame, random=~IV3|speaker) summary(x2) #nested random effect x5 <- lme (DV ~ IV1 + IV2 + IV1*IV2, data=a.frame, random=~1|speaker/item) summary(x5) ``` What I really would like to do is having a model with both speaker and item as random effects separately. I had tried to use this formula: ``` x4 <- lme (DV ~ IV1 + IV2 + IV1*IV2, data=a.frame, random=~1|speaker + 1|item) ``` However, this formula gives me the following warning message: ``` Warning message: In Ops.factor(speaker, 1) : + not meaningful for factors ``` Do you have any idea what this means? And how can I fit both speaker and item as random effects separately?