删除 ggplot2 中的额外图例 [英] Remove extra legends in ggplot2

问题描述

我有一个简单的数据框，我正在尝试使用 ggplot2 绘制组合线图和点图.假设我的数据如下所示:

I have a simple data frame that I'm trying to do a combined line and point plot using ggplot2. Supposing my data looks like this:

df <- data.frame(x=rep(1:10,2), y=c(1:10,11:20), 
                 group=c(rep("a",10),rep("b",10)))

我正在尝试制作一个情节:

And I'm trying to make a plot:

g <- ggplot(df, aes(x=x, y=y, group=group))
g <- g + geom_line(aes(colour=group))
g <- g + geom_point(aes(colour=group, alpha = .8))
g

结果看起来不错，但有一个例外.它有一个额外的图例，显示了我的 geom_point 层的 alpha.

The result looks fine with one exception. It has an extra legend showing the alpha for my geom_point layer.

如何让图例显示组颜色，而不是显示我的 alpha 设置的颜色?

How can I keep the legend showing group colors, but not the one that shows my alpha settings?

推荐答案

美学可以在 ggplot 调用中设置或映射.

Aesthetics can be set or mapped within a ggplot call.

• aes(...) 中定义的美学是从数据中映射，并创建一个图例.
• 美学也可以设置为单个值，方法是在aes()之外定义它.

• An aesthetic defined within aes(...) is mapped from the data, and a legend created.
• An aesthetic may also be set to a single value, by defining it outside aes().

在这种情况下，您似乎希望 set alpha = 0.8 和 map colour = group.

In this case, it appears you wish to set alpha = 0.8 and map colour = group.

要做到这一点，

将 alpha = 0.8 放在 aes() 定义之外.

Place the alpha = 0.8 outside the aes() definition.

g <- ggplot(df, aes(x = x, y = y, group = group))
g <- g + geom_line(aes(colour = group))
g <- g + geom_point(aes(colour = group), alpha = 0.8)
g

对于任何映射变量，您可以通过在适当的scale_...中使用guide = 'none'来抑制图例的出现称呼.例如.

For any mapped variable you can supress the appearance of a legend by using guide = 'none' in the appropriate scale_... call. eg.

g2 <- ggplot(df, aes(x = x, y = y, group = group)) + 
        geom_line(aes(colour = group)) +
        geom_point(aes(colour = group, alpha = 0.8))
g2 + scale_alpha(guide = 'none')

哪个将返回相同的情节

编辑@Joran 的评论很准确，我的回答更全面

EDIT @Joran's comment is spot-on, I've made my answer more comprehensive

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