Removing ggplot2's geom_point icons from the legend
问题 注意:这是对这个问题的跟进。 首先是重现数据的代码: mydf <- data.frame(year = c(rep(2000, 3), rep(2002, 3), rep(2004, 3), rep(2006, 3), rep(2008, 3), rep(2010, 3), rep(2012, 3), rep(2014, 3), rep(2016, 3)), answer = rep(c("A great deal", "Hardly any", "Only some"), 9), result = c(0.3015940, 0.1399303, 0.5584757, 0