ggplot 输出中的错误图例

Question

此代码的输出给出了一个分布和两条垂直线，一条是红色，一条是蓝色。但在图例中，蓝线标记为 "red"，反之亦然。可能是什么原因？ Distribution and 2 vertical lines

variances <- apply(matrix(rexp(40*1000,0.2),1000),1,var) 
hist(variances)
v_theo <- 45 ## need to define v_theo
g <- ggplot(data.frame(x=variances), aes(x = x)) 
g <- g + geom_density(alpha=0.2,size=1,fill="red")
g <- g + geom_vline(aes(xintercept = mean(variances),color="red"), size=1) 
g <- g + geom_vline(aes(xintercept = (v_theo),color="blue"), size=1) 
g

Answer 1

那是因为颜色是由 aes 函数映射的。如果您想手动映射它们，您可以像这样

将它们从 aes 中取出

variances <- apply(matrix(rexp(40*1000,0.2),1000),1,var) 
hist(variances)
g <- ggplot(data.frame(x=variances), aes(x = x)) 
g <- g + geom_density(alpha=0.2,size=1,fill="red")
g <- g + geom_vline(aes(xintercept = mean(variances)), color="red", size=1) 
g <- g + geom_vline(aes(xintercept = (v_theo)), color="blue", size=1) 
g

虽然这样做你会失去传说。如果你想要图例，你可以使用 scale_color_manual 来固定颜色的顺序。

variances <- apply(matrix(rexp(40*1000,0.2),1000),1,var) 
hist(variances)
g <- ggplot(data.frame(x=variances), aes(x = x)) 
g <- g + geom_density(alpha=0.2,size=1,fill="red")
g <- g + geom_vline(aes(xintercept = mean(variances),color="red"), size=1) 
g <- g + geom_vline(aes(xintercept = (v_theo),color="blue"), size=1) 
g <- g + scale_color_manual(values = c("blue", "red"))
g

Answer 2

library(ggplot2)
variances <- apply(matrix(rexp(40*1000,0.2),1000),1,var) 
hist(variances)
v_theo <- 45


g <- ggplot(data.frame(x=variances), aes(x = x)) 
g <- g + geom_density(alpha=0.2,size=1,fill="red")
g <- g + geom_vline(aes(xintercept = v_theo, color="blue"), size=1) 
g

g <- ggplot(data.frame(x=variances), aes(x = x)) 
g <- g + geom_density(alpha=0.2,size=1,fill="red")
g <- g + geom_vline(aes(xintercept = mean(variances),color="mean"), size=1) 
g <- g + geom_vline(aes(xintercept = v_theo,color="v_theo"), size=1) +
  scale_color_manual(name = "Legend name", values = c(mean = "red", v_theo = "blue"))
g

另见此处：

ggplot 输出中的错误图例

Wrong legend in ggplot output

r

ggplot2

geom-vline