ggplot geom_point（）使用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

我试图用三种不同颜色绘制三个数值范围的数据点。例如：

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

以上产生：

现在，我想对此进行修改，使qseq值<17为黑色，17-19之间的值为黄色，19以上的值为红色。我尝试了各种方法，但它们都没有效果：

• 取自看起来很有前途，但是我无法让他们使用 geom_point（）。

。


• 各种类似的帖子也是如此，例如侧栏中列出的帖子。
  
  
  

  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（black，yellow，red）） 
  错误：手动缩放值不足，需要30个，但只提供了4个
    

  我是猜测我会以某种方式使用 cut（）或 factor（），但我似乎无法弄清楚。任何建议？

  解决方案

  您需要将 cut ：
  
  

    library（ggplot2）
   ggplot（mtcars，aes（wt，mpg））+ 
   geom_point （aes（color = cut（qsec，c（-Inf，17,19，Inf））），
   size = 5）+ 
   scale_color_manual（name =qsec，
   values = c（（ -  Inf，17）=bl ack，
  （17,19）=黄色，
  （19，Inf）=红色），
   labels = 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_gradientn(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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