r - 在 geom_point 中为 ggplot2 中的负值和正值设置不同的颜色

Question

给定如下数据框:

df <- data.frame(city = c("bj", "sh", "gz", "sz"),
                 price = c(12, 7, 5, 6),
                 pct = c(-2.3, 5, -4, 4), stringsAsFactors=FALSE)

输出:

  city  price  pct
0   bj     12 -2.3
1   sh      7  5.0
2   gz      5 -4.0
3   sz      6  4.0

我想用ggplot画图:barchart代表city，point代表pct，但是我想要对负值和正值使用不同的颜色。

我如何在 ggplot2 中做到这一点？

代码:

ggplot(df, aes(fill = city, y = price, x = city)) + 
    geom_bar(position = "dodge", stat = "identity", alpha = 0.5, fill = "#FF6666") +
    geom_point(data = df,  aes(x = city, y = pct), size = 2)

Answer 1

您可以使用 pct>0 作为颜色(0 或 1 取决于 pct 的符号)并将 city 转换为一个因子:

ggplot(df, aes(fill = city, y = price, x = city)) + 
    geom_bar(position = "dodge", stat = "identity", alpha = 0.5, fill = "#FF6666") +
    geom_point(data = df,  aes(x = factor(city), y = pct, color = pct>0), size = 2)