编织文档导致 seq.int 错误

Question

编织我的文档时，以下代码停止编织并导致错误。值得注意的是，在正常操作中，此代码通过显示所需的图形来工作。仅在编织文档时出现此问题。

我试图插入 echo=false 希望绕过这个问题，但最终得到了同样的错误信息。

代码：

qplot(wt, mpg, data=mtcars, colour=factor(am)) +
  geom_smooth(aes(ymin = lcl, ymax = ucl), data=grid, stat="identity") +
  ggtitle("MPG, Weight, & Transmission Relationship")

错误：

Quitting from lines 131-134 (MotorTrend.Rmd) 
Error in seq.int(U[1L], U[2L], length.out = nx + 1) : 
  'length.out' must be a non-negative number
Calls: <Anonymous> ... lapply -> FUN -> <Anonymous> -> f -> <Anonymous> -> f

Execution halted

Answer 1

我必须更好地定义我的术语，所以我添加了额外的代码：

model <- lm(mpg ~ wt + factor(am) + wt*factor(am), data=mtcars)
grid <- with(mtcars, expand.grid(
  wt = seq(min(wt), max(wt), length = 20),
  am = levels(factor(am))))
grid$mpg <- stats::predict(model, newdata=grid)

err <- stats::predict(model, newdata=grid, se = TRUE)
grid$ucl <- err$fit + 1.96 * err$se.fit
grid$lcl <- err$fit - 1.96 * err$se.fit
qplot(wt, mpg, data=mtcars, colour=factor(am)) +
  geom_smooth(aes(ymin = lcl, ymax = ucl), data=grid, stat="identity") +
  ggtitle("MPG, Weight, & Transmission Relationship")

编织文档导致 seq.int 错误

Knit Document Results in Error in seq.int

r

ggplot2

rstudio

knitr

r-markdown