如何在 R 中使用 ggplot2 为点着色？

Question

I am attempting to graph two variables and then use a gradient colour scheme for visual emphasis - however, it keeps giving me a black scatterplot as if I didn't type the command.

Fake Dataset:

Nature_DR = data.frame(Protect_LGA = runif(100, min=0, max=87.5),
                       DR_2011_Protect = runif(100, min=3, max=10))

Here is my code

    ggplot(Nature_DR, aes(x=Protect_LGA, y=DR_2011_Protect)) +
      geom_point() + 
      scale_fill_gradient(low="yellow", high ="green") + 
      geom_smooth(method = 'loess') +
      coord_cartesian(xlim = c(0,87.5), ylim = c(3,10)) + 
      labs(x="Proportion of LGA that is protected", 
           y = "Standardised Death Rates in 2011",
           title = "Relation between Protected Areas and Death Rates")

Answer 1

You have asked ggplot to apply a color gradient to the fill aesthetic, but you have not specified a fill aesthetic. In addition, geom_point() does not use the fill aesthetic, it uses the color aesthetic.

So, for example, you could color the points by DR_2011_Protect using the following, which will use the default color gradient:

   ggplot(Nature_DR, aes(x=Protect_LGA, y=DR_2011_Protect, color=DR_2011_Protect)) +
     geom_point()

Or apply your color gradient to the points by changing which scale you modify:

   ggplot(Nature_DR, aes(x=Protect_LGA, y=DR_2011_Protect, color=DR_2011_Protect)) + 
     geom_point() + 
     scale_color_gradient(low="yellow", high ="green")