With the following dataset...
Subj <- rep(1:10, each = 10)
Item <- rep(1:10, times = 10)
IV1 <- rep(1:5, times = 20)
DV <- rnorm(100)
library(data.table)
data <- as.data.table(cbind(Subj, Item, IV1, DV))
data$Subj <- as.factor(data$Subj)
data$Item <- as.factor(data$Item)
data$IV1 <- as.factor(data$IV1)
library(MASS)
contrasts(data$IV1) <- contr.sdif(5)
library(lme4)
m1 <- lmer(DV ~ IV1 + (1 + IV1|Subj) + (1|Item), data = data)
Now suppose that it turned out that there was only variance in the random subject slope for the contrast of IV1 level 2 vs. IV1 level1. Is it possible to fit a random slope only for this contrast?
