如何手动控制ggplot2图例

Question

我正在尝试为此代码生成的qplot添加图例：

qplot(pa1, geom = "density", fill = I("blue"), alpha = I(0.3), label = "auto") + geom_density(aes(x = pb1), fill = "red", alpha = I(0.3), label = "brand") + 
  geom_density(aes(x = ph1), fill = "green", alpha = I(0.3)) + xlab("Predicted Values") + 
  ylab("Density") + ggtitle("Auto (blue) Brand (red) and Home (green)")

其中pa1, pb1, ph1是来自glm模型的预测向量。

最终输出有效：

但没有传说......

Answer 1

你可能会发现这样做更简单，传说就在那里。

ggplot(diamonds) + geom_density(aes(x=price, colour=clarity,fill=clarity,alpha=.3))