我有以下 Dataframe 和拟合模型：

goyo <- data.frame(
  Grade <- c(8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 6, 8, 8, 8, 7, 7, 7, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8),
  a <- c(NA, 0, NA, NA, NA, NA, NA, NA, NA, NA, 1, NA, 1, 1, NA, 1, NA, 1, NA, 1, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA),
  b <- c(0, NA, NA, NA, NA, NA, NA, NA, 0, NA, NA, NA, NA, 0, NA, NA, NA, 1, NA, NA, 1, NA, 0, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA)
)
goyo$Grade <- factor(goyo$Grade)
glm(reformulate(c("Grade"), "a"), family=binomial, data = goyo)
glm(reformulate(c("Grade"), "b"), family=binomial, data = goyo)

字符串
当我运行“B”列的拟合模型时，我得到错误：

Error in `contrasts<-`(`*tmp*`, value = contr.funs[1 + isOF[nn]]) : 
  contrasts can be applied only to factors with 2 or more levels

型
这看起来像是与水平的数量有关。然而，这两列看起来几乎相同，我不明白它们之间的区别是什么，使它们给予不同的结果。