相关疑难解决方法(0)

说我想在ggplot中绘制两个图层,一个包含点,另一个包含线条,如果满足某个条件.

没有标准的代码可能如下所示:

library("ggplot2")

# Summarise number of movie ratings by year of movie
mry <- do.call(rbind, by(movies, round(movies$rating), function(df) {
  nums <- tapply(df$length, df$year, length)
  data.frame(rating=round(df$rating[1]), year = as.numeric(names(nums)), number=as.vector(nums))
}))

p <- ggplot(mry, aes(x=year, y=number, group=rating))

p + 
geom_point()+
geom_line()

现在绘制点而不仅仅是线条的条件是,一个名为tmp.data的对象不等于表达式"无值".

tmp.data<-c(1,2,3) # in this case the condition is fulfilled

# attempt to plot the two layers including the condition in the plotting function
p+ 
  if(tmp.data[1]!="no value"){ geom_point()+}
  geom_line()

失败....

Error: unexpected '}' in:
"p+ 
if(tmp.data[1]!="no value"){ geom_point()+}"

geom_line()geom_line: …