为直方图的垂直线添加图例

Question

我正在尝试为要创建的图形添加图例。想法是比较偏斜和对称分布的均值和中位数。这是我目前拥有的代码，但是

show.legend = TRUE 

代码不起作用。

set.seed(19971222)

sym <- as.data.frame(cbind(c(1:500), rchisq(500, df = 2))) # generate 500 random numbers from a symetric distribution
colnames(sym) <- c("index", "rnum")

sym_mean <- mean(sym$rnum)
sym_med <- median(sym$rnum)
# get into a format that tidyverse likes
central_measures <- as.data.frame(cbind(sym_mean, sym_med))
colnames(central_measures) <- c("mean", "median")

sym %>% ggplot(aes(sym$rnum)) + 
  geom_histogram(binwidth = 0.4, fill = "steelblue", colour = "navy", alpha = 0.9) + 
  geom_vline(xintercept = sym_mean, colour = "red", show.legend = TRUE) + 
  geom_vline(xintercept = sym_med, colour = "yellow", show.legend = TRUE) + 
  labs(title = "Histogram of 500 Randomly Generated Numbers from the Chi-Squared Distribution", 
       x = "Value", 
       y = "Frequency") +
  theme_minimal()

我只想在侧面画一个图例，说红色是“平均值”，黄色是“中位数”。

谢谢！

Answer 1

嘿，对不起，我被跟踪了一下，而我的第一个建议有些偏离。这是一种实现为中心度度量添加图例的方法。

# use this instead of central_measures
central_values <- data.frame(measurement = c("mean", "median"),
                             value = c(sym_mean, sym_med))

sym %>% ggplot(aes(sym$rnum)) + 
  geom_histogram(binwidth = 0.4, fill = "steelblue", colour = "navy", alpha = 0.9) + 
  geom_vline(data = central_values, aes(xintercept = value, color = measurement)) +
  scale_color_manual(values = c("red", "orange"), name = NULL) +
  labs(title = "Histogram of 500 Randomly Generated Numbers from the Chi-Squared Distribution", 
       x = "Value", 
       y = "Frequency") +
  theme_minimal()

如果您还有其他麻烦，请告诉我，再次对不起您使我误入歧途！