求助各位！
R语言新手，想线性混合模型分析，数据：center和disease是分类变量，FP和Q5是连续变量。模型：Q5是应变量，disease、FP和两者的交互效应设为固定效应，center设为随机效应，包括截距和与FP的交互效应。
代码如下：
> library(readxl)
> Q5 <- read_excel("LNR5.xlsx", col_types = c("text",
+     "text", "numeric", "numeric"))
> View(Q5)
> which(is.na(Q5)==T)
integer(0)
> library(Matrix)
> library(lme4)
> Q5.model = lmer(Q5 ~ disease + FP + FP|disease + (1 + FP|center),data=Q5)

结果提示如下错误，请问有人知道这是什么意思和如何解决么？
Error: Invalid grouping factor specification, disease + (1 + FP | center)
In addition: Warning messages:
1: In Ops.factor(1, FP) : ‘+’ not meaningful for factors
2: In Ops.factor(1 + FP, center) : ‘|’ not meaningful for factors
3: In Ops.factor(disease, (1 + FP | center)) :
  ‘+’ not meaningful for factors