为一组点线图和垂直线图提供单独的图例 [英] Have separate legends for a set of point-line plots, and a vertical line plot

问题描述

示例数据框(如果有更好/更惯用的方法，请告诉我):

Example data frame (if there's a better/more idiomatic way to do this, let me know):

n <- 10  
group <- rep(c("A","B","C"),each = n)
x   <- rep(seq(0,1,length = n),3)
y   <- ifelse(group == "A",1+x,ifelse(group == "B",2+2*x,3+3*x))
df  <- data.frame(group,x,y)
xd  <- 0.5
des <- data.frame(xd)

我想为df中的数据绘制创建点线图，在xd指示的x位置添加一条垂直曲线，并为两者获取可读的图例.我尝试了以下方法:

I want to plot create point-line plots for the data in df, add a vertical curve at the x location indicated by xd, and get readable legends for both. I tried the following:

p <- ggplot(data = df, aes(x = x, y = y, color = group)) + geom_point() + geom_line(aes(linetype=group))
p <- p + geom_vline(data = des, aes(xintercept = xd), color = "blue")
p

不完全是我的想法，垂直线没有传说.

Not quite what I had in mind, there's no legend for the vertical line.

一个小的修改(我不明白为什么 geom_vline 是少数具有 show.legend 参数的几何之一，而且默认为 FALSE!):

A small modification (I don't understand why geom_vline is one of the few geometries with a show.legend parameter, which moreover defaults to FALSE!):

p <- ggplot(data = df, aes(x = x, y = y, color = group)) + geom_point() + geom_line(aes(linetype=group))
p <- p + geom_vline(data = des, aes(xintercept = xd), color = "blue", show.legend = TRUE)
p   

至少现在垂直条显示在图例中，但我不希望它与 group 进入相同的类别"(?).我想要另一个图例条目，标题为 Design，并且只包含垂直线.我怎样才能做到这一点?

At least now the vertical bar is showing in the legend, but I don't want it to go in the same "category" (?) as group. I would like another legend entry, titled Design, and containing only the vertical line. How can I achieve this?

推荐答案

一种可能的方法是添加一个额外的虚拟美学，如 fill =，我们随后将使用它来创建第二个图例与 scale_fill_manual() 结合:

A possible approach is to add an extra dummy aesthetic like fill =, which we'll subsequently use to create the second legend in combination with scale_fill_manual() :

ggplot(data = df, aes(x = x, y = y, color = group)) + 
        geom_point() + 
        geom_line(aes(linetype=group), show.legend = TRUE) + 
        geom_vline(data = des, 
                   aes(xintercept = xd, fill = "Vertical Line"), # add dummy fill
                   colour = "blue") +
        scale_fill_manual(values = 1, "Design", # customize second legend 
                guide = guide_legend(override.aes = list(colour = c("blue"))))

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