set.seed(1)

x <- rnorm(100)?

f <- rep(0:1, each = 50)?

y <- x + f - f*x + rnorm(100, sd = 0.5)?

f <- factor(f, labels = c("Group1", "Group2"))?

xyplot(y~x | f, layout(2,1))?

然后為啥出現錯誤？?

Error in layout(2, 1) : layout matrix must contain at least one reference to each of the values {1 ... 2}