ggplot geom_point() 具有基于特定离散值的颜色 [英] ggplot geom_point() with colors based on specific, discrete values

问题描述

我正在尝试为三个值范围绘制具有三种不同颜色的数据点.例如:

库(ggplot2)ggplot(mtcars, aes(wt, mpg)) + geom_point(aes(colour = qsec))

以上产生:

现在，我想修改它，使 qseq 值 <17 为黑色，17 到 19 之间的值为黄色，19 以上的值为红色.我尝试了各种方法，但它们似乎都不起作用:

• 取自中给出的解决方案似乎很有希望，但我无法得到它们使用 geom_point().

• 同样适用于各种类似的帖子，例如边栏中列出的帖子.

我意识到我可能需要使用某种离散比例而不是 scale_fill_gradientn 但我尝试使用 scale_color_manual() 失败:

ggplot(mtcars, aes(wt, mpg)) + geom_point(aes(color = factor(qsec))) +scale_color_manual(values=c(黑色"，黄色"，红色")错误:手动刻度值不足.需要30个，但只提供了4个.

我猜我将不得不以某种方式使用 cut() 或 factor() 但我似乎无法弄清楚如何使用.有什么建议吗?

解决方案

你需要cut你的值到区间:

库(ggplot2)ggplot(mtcars, aes(wt, mpg)) +geom_point(aes(colour = cut(qsec, c(-Inf, 17, 19, Inf))),大小 = 5) +scale_color_manual(name = "qsec",values = c("(-Inf,17]" = "黑色","(17,19]" = "黄色","(19, Inf]" = "红色"),标签 = c("<= 17", "17 < qsec <= 19", "> 19"))

I am trying to plot data points with three different colors for three value ranges. For example:

library(ggplot2)
ggplot(mtcars, aes(wt, mpg)) + geom_point(aes(colour = qsec))

The above produces:

Now, I would like to modify this so that qseq values <17 are black, values between 17 and 19 are yellow and values above 19 are red. I've tried various approaches, but none of them seems to work:

• Taken from here

    ggplot(mtcars, aes(wt, mpg)) + geom_point(aes(fill = qsec)) + 
    scale_fill_gradient(colours = c("black","yellow","red"), 
    breaks=c(0,17,19), labels = format(c("0","17","19")))
  

This produces:

So, the colorbar seems correct but the colors are not actually applied.

• The solutions given in ggplot2 heatmap with colors for ranged values seem promising but I can't get them to work with geom_point().

• Same goes for various similar posts such as those listed in the sidebar.

I realize I will probably need to use some kind of discrete scale instead of scale_fill_gradientn but my attempts to use scale_color_manual() fail:

ggplot(mtcars, aes(wt, mpg)) + geom_point(aes(color = factor(qsec))) + 
scale_color_manual(values=c("black", "yellow","red")
Error: Insufficient values in manual scale. 30 needed but only 4 provided.

I am guessing I will somehow have to use cut() or factor() but I can't seem to figure out how. Any suggestions?

解决方案

You need to cut your values into intervals:

library(ggplot2)
ggplot(mtcars, aes(wt, mpg)) + 
  geom_point(aes(colour = cut(qsec, c(-Inf, 17, 19, Inf))),
             size = 5) +
  scale_color_manual(name = "qsec",
                     values = c("(-Inf,17]" = "black",
                                  "(17,19]" = "yellow",
                                  "(19, Inf]" = "red"),
                     labels = c("<= 17", "17 < qsec <= 19", "> 19"))

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