使用R / ggplot2控制中间值颜色与scale_colour_continuous [英] Control middle value colours with scale_colour_continuous using R/ggplot2

问题描述

我有一组数据，并希望将颜色映射到某种参考值，如下所示：

• 以下的值为红色


• 接近的值为蓝色


• >
  

我还想表明这些值是连续的，所以只需使用 cut / code>并使用 scale_colour_discrete 不是我要找的。下面是一些示例数据：

  set.seed（123）
x < -  runif（100，min = max = 10）
y<  -  runif（100，min = 1，max = 10）
 test<  -  data.frame（x = x，y = y）
 test $ color < runif（100，min = 1，max = 10）
 ggplot（test，aes（x = x，y = y，color = color））+ geom_point（size = 3）
  

这会产生以下结果：

我熟悉 scale_colour_gradient（low =red，high =green），但我希望更有意识地沿着期望的值映射转换我的颜色，使得区域更流畅。间距不一定是线性的。换句话说，对于参考值3，映射将是这样：

 值：1 3 10 
 color：red blue green 
  

这是否可能？我也会采取替代的解决方案，以完成一个良好的可视化，突出理想值很容易在一点点。例如，我考虑替换参考附近的值，使（ref-tol ，然后使用 scale_colour_gradient 的选项为 na.value 。

考虑 cut（）选项，只是一个非常小的剪切尺寸，然后找出如何逐渐更改颜色沿着结果中断？

解决方案

从 http： //docs.ggplot2.org/0.9.2.1/scale_gradient2.html ：

  scale_color_gradient2（low =red ，midpoint = 3，mid =blue，high =green）
  

UPDATE： / p>

关于OP的评论 - 玩中点和 space =Lab有助于：

＃使用Lab颜色空间也可以提高知觉属性
＃以稍慢的操作价格
d + scale_colour_gradient2（space =Lab ）


I have a set of data and would like to map the colour aesthetic around a sort of "reference value" like so:

• values below are red
• values near are blue
• values above are green

I still want to show the fact that values are on a continuoum, so simply using a function like cut() and using scale_colour_discrete is not what I'm looking for. Here's some example data:

set.seed(123)
x <- runif(100, min = 1, max = 10)
y <- runif(100, min = 1, max = 10)
test <- data.frame(x = x, y = y)
test$colour <- runif(100, min = 1, max = 10)
ggplot(test, aes(x = x, y = y, colour = colour)) + geom_point(size = 3)

That produces the following:

I'm familiar with scale_colour_gradient(low = "red", high = "green"), however I was hoping to more deliberately transition my colours along desired value mapping to make the regions "pop" a bit more visually. Spacing would not necessarily be linear. in other words, for a reference value of 3, the mapping would be something like this:

value:  1     3      10
colour: red   blue   green

Is this possible? I'd also take alternative solutions to accomplish a good visualization to highlight "desirable" values easily among a sea of points. For example, I considered replacing values near the reference such that (ref - tol < colour < ref + tol) <- NA, and then using scale_colour_gradient's option for na.value.

Or should I truly be considering the cut() option, just with a very small cut size and then figure out how to gradually change the colours along the resultant breaks?

解决方案

From http://docs.ggplot2.org/0.9.2.1/scale_gradient2.html:

scale_color_gradient2(low = "red", midpoint = 3, mid = "blue", high = "green")

UPDATE:

Concerning OP's comment - playing around with midpoints and space="Lab" helps:

# Using the Lab colour space also improves perceptual properties
# at the price of slightly slower operation
d + scale_colour_gradient2(space="Lab")

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