根据y值连续颜色的geom_line [英] Continuous colour of geom_line according to y value

问题描述

如果你看看这个

  ggplot（mtcars，aes（x = disp，y = mpg，color = mpg））+ geom_line（） 
  

您将会看到线条颜色根据相应的y值而变化，这就是我想要的，但只是逐节。我希望颜色根据y值连续变化。任何简单的方法？

解决方案

想到的一种可能是使用插值来创建更多的x值和y值，从而使颜色更连续。我使用 approx 来线性插入给定的数据点。下面是一个简单数据集的例子：

 ＃原始数据和相应的图
 df < -  data.frame （x = 1：3，y = c（3,1,4））
 library（ggplot2）
 ggplot（data = df，aes（x = x，y = y，color = y） ）+ 
 geom_line（size = 3）
  

 ＃插值使'更多值和更平滑的颜色梯度
 vals < -  approx（x = df $ x，y = df $ y）
 df2 < -  data.frame（x = vals $ x，y = vals $ y）
 
 ggplot（data = df2，aes（x = x，y = y，color = y））+ 
 geom_line（size = 3）
  

n 参数中使用 approx 来调整要创建的点数（插值发生在 n 跨越区间[ min（x），max（x）]）的等间隔点。有了更多的值，可能 geom_point 的外观更平滑：



  vals < -  approx（x = df $ x，y = df $ y，n = 500）
 df2 < -  data.frame（x = vals $ x，y = vals $ y）
 ggplot（data = df2，aes（x = x，y = y，color = y））+ 
 geom_point（size = 3）
  




If you look at this

ggplot(mtcars,aes(x=disp,y=mpg,colour=mpg))+geom_line()

you will see that the line colour varies according to the corresponding y value, which is what I want, but only section-by-section. I would like the colour to vary continuously according to the y value. Any easy way?

解决方案

One possibility which comes to mind would be to use interpolation to create more x- and y-values, and thereby make the colours more continuous. I use approx to " linearly interpolate given data points". Here's an example on a simpler data set:

# original data and corresponding plot
df <- data.frame(x = 1:3, y = c(3, 1, 4))
library(ggplot2)
ggplot(data = df, aes(x = x, y = y, colour = y)) +
  geom_line(size = 3)

# interpolation to make 'more values' and a smoother colour gradient 
vals <- approx(x = df$x, y = df$y)
df2 <- data.frame(x = vals$x, y = vals$y)

ggplot(data = df2, aes(x = x, y = y, colour = y)) +
  geom_line(size = 3)

If you wish the gradient to be even smoother, you may use the n argument in approx to adjust the number of points to be created ("interpolation takes place at n equally spaced points spanning the interval [min(x), max(x)]"). With a larger number of values, perhaps geom_point gives a smoother appearance:

vals <- approx(x = df$x, y = df$y, n = 500)
df2 <- data.frame(x = vals$x, y = vals$y)
ggplot(data = df2, aes(x = x, y = y, colour = y)) +
  geom_point(size = 3)

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