在图上使用多行将图例添加到ggplot2 [英] Adding legend to ggplot2 with multiple lines on plot

问题描述

我真的很感谢您的帮助.我完全不了解ggplot2如何思考传说！

I would really appreciate some help with this. I completely do not understand how ggplot2 is thinking about legends!

该图表基于名为"meltdf"的以下数据框:

The chart is based on the following data frame, called "meltdf":

        xval       variable  value
1   0.000000 Shortfall Risk 100.00
2   4.624457 Shortfall Risk  99.83
3   9.179656 Shortfall Risk  60.96
4  13.742579 Shortfall Risk  36.29
5  18.620338 Shortfall Risk  27.71
6  22.947704 Shortfall Risk  22.52
7  27.690638 Shortfall Risk  19.72
8  32.174379 Shortfall Risk  17.89
9  36.637940 Shortfall Risk  15.79
10 41.107962 Shortfall Risk  15.96
11 45.644065 Shortfall Risk  15.97

图表绘制如下:

ggplot(data=meltdf,aes(x=xval,y=value))+
  geom_line(size=1,colour=rgb(69,99,111,max=255))+
  geom_vline(xintercept = 22 ,colour="darkgray")+
  geom_vline(xintercept = 30 ,colour="darkred")+
  theme_bw()+
  labs(title="Shortfall Risk versus Investment Risk, Meeting Expenditure Only")+
  theme(legend.position="bottom",
    legend.text = element_text(size=9),
    axis.text = element_text(size=9),
    axis.title = element_text(size=9),
    plot.title=element_text(size = 9),
    legend.title=element_text(size=9))+
  labs(x="Largest Historical Decline (%)", y="Probability of Shortfall (%)")+
  scale_y_continuous(limits = c(0, 100))

我想在底部有一个图例，图中的所有三行(蓝色，红色和灰色)均被命名.

I would like to have a legend at the bottom in which all three lines in the chart (blue, red and grey) are named.

推荐答案

ggplot将自动为映射在aes()调用中的元素(颜色，线型等)生成图例.这意味着当您手动指定元素的颜色时，就像在这里一样(所有colour语句都不在aes内)，您将不会得到图例.

ggplot will automatically produce legend for the elements (colours, linetype, etc.) that are mapped inside an aes() call. It means that you will not get a legend when you manually specify the colour of an element, like you do here (all your colour statements are not inside aes).

我建议您将垂直线的坐标存储在其自己的数据框中，在此处可以将其映射到给出其颜色的变量.在这里，我创建了这样一个数据框(summ)，并将您的代码重写为geom_vline().我还将meltdf$variable映射到geom_vline中的colour，因此它出现在图例中.最后，我添加了scale_colour_manual()选择颜色.您可能需要调整summ$colour的值，以便它们在图例中有意义.

I recommend you store the coordinates of your vertical lines in their own dataframe, where they can be mapped to a variable giving their color. Here, I create such a dataframe (summ) and rewrote your code for geom_vline(). I also mapped meltdf$variable to colour in geom_vline so it appears in the legend. Finally, I added scale_colour_manual() to choose the colours. You may want to adapt the value of summ$colour so they make sense in the legend.

summ <- data.frame(x=c(22,30),
                   colour=c("gray","red"))

ggplot(data=meltdf,aes(x=xval,y=value))+
  geom_line(size=1,aes(colour=variable))+
  geom_vline(data=summ,aes(xintercept = x,colour=colour))+
  scale_color_manual(values = c(rgb(69,99,111,max=255),"darkgray","darkred")) +
  theme_bw()+
  labs(title="Shortfall Risk versus Investment Risk, Meeting Expenditure Only")+
  theme(legend.position="bottom",
        legend.text = element_text(size=9),
        axis.text = element_text(size=9),
        axis.title = element_text(size=9),
        plot.title=element_text(size = 9),
        legend.title=element_text(size=9))+
  labs(x="Largest Historical Decline (%)", y="Probability of Shortfall (%)")+
  scale_y_continuous(limits = c(0, 100))

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