R-平滑颜色并向散点图添加图例 [英] R - Smoothing color and adding a legend to a scatterplot

问题描述

我在R中有一个散点图.每个(x,y)点都根据其z值着色.因此，您可以将每个点视为(x,y,z)，其中(x,y)确定其位置，而z确定其沿颜色渐变的颜色.我想补充两件事

I have a scatterplot in R. Each (x,y) point is colored according to its z value. So you can think of each point as (x,y,z), where (x,y) determines its position and z determines its color along a color gradient. I would like to add two things

1. 右侧的图例显示颜色渐变，什么z值对应什么颜色
2. 我想我想使用某种类型的插值对所有颜色进行平滑处理.换句话说，整个绘图区域(或至少大部分区域)都应着色，以便看起来像一个巨大的热图，而不是散点图.因此，在下面的示例中，周围将有很多橙色/黄色，然后是一些紫色的斑点.如果需要，我很高兴进一步澄清我要在此处解释的内容.

1. A legend on the right side showing the color gradient and what z values correspond to what colors
2. I would like to smooth all the color using some type of interpolation, I assume. In other words, the entire plotting region (or at least most of it) should become colored so that it looks like a huge heatmap instead of a scatterplot. So, in the example below, there would be lots of orange/yellow around and then some patches of purple throughout. I'm happy to further clarify what I'm trying to explain here, if need be.

这是我当前拥有的代码以及它生成的图像.

Here is the code I have currently, and the image it makes.

x <- seq(1,150)
y <- runif(150)
z <- c(rnorm(mean=1,100),rnorm(mean=20,50))
colorFunction <- colorRamp(rainbow(100))
zScaled <- (z - min(z)) / (max(z) - min(z))
zMatrix <- colorFunction(zScaled)
zColors <- rgb(zMatrix[,1], zMatrix[,2], zMatrix[,3], maxColorValue=255)
df <- data.frame(x,y)
x <- densCols(x,y, colramp=colorRampPalette(c("black", "white")))
df$dens <- col2rgb(x)[1,] + 1L
plot(y~x, data=df[order(df$dens),],pch=20, col=zColors, cex=1)

推荐答案

以下是一些使用ggplot2软件包的解决方案.

Here are some solutions using the ggplot2 package.

# Load library
library(ggplot2)

# Recreate the scatterplot from the example with default colours
ggplot(df) +
  geom_point(aes(x=x, y=y, col=dens))

# Recreate the scatterplot with a custom set of colours. I use rainbow(100)
ggplot(df) +
  geom_point(aes(x=x, y=y, col=dens)) +
  scale_color_gradientn(colours=rainbow(100))

# A 2d density plot, using default colours
ggplot(df) +
  stat_density2d(aes(x=x, y=y, z=dens, fill = ..level..), geom="polygon") +
  ylim(-0.2, 1.2) + xlim(-30, 180) # I had to twiddle with the ranges to get a nicer plot

# A better density plot, in my opinion. Tiles across your range of data
ggplot(df) +
  stat_density2d(aes(x=x, y=y, z=dens, fill = ..density..), geom="tile", 
                 contour = FALSE)

# Using custom colours. I use rainbow(100) again.
ggplot(df) +
  stat_density2d(aes(x=x, y=y, z=dens, fill = ..density..), geom="tile", 
                 contour = FALSE) +
  scale_fill_gradientn(colours=rainbow(100))

# You can also plot the points on top, if you want
ggplot(df) +
  stat_density2d(aes(x=x, y=y, z=dens, fill = ..density..), geom="tile", 
                 contour = FALSE) +
  geom_point(aes(x=x, y=y, col=dens)) +
  scale_colour_continuous(guide=FALSE) # This removes the extra legend

我也附上了情节:

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