How to color only for points above and below certain amounts in ggplot2?

user_12265759 0
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So I have a reproducible code below, I only want to color the points below and above the dotted black lines and nothing in between. The points in between should be grey or whatever default color without aes(color = x)

color_above <- mean(iris$Sepal.Width) + sd(iris$Sepal.Width)
color_below <- mean(iris$Sepal.Width) - sd(iris$Sepal.Width)


ggplot(data=iris, aes(x = Sepal.Length, y = Sepal.Width)) + geom_point(aes(color=Species, shape=Species)) +
  xlab("Sepal Length") +  ylab("Sepal Width")+
  geom_hline(yintercept = color_above, linetype = "dashed", color = "black") +
  geom_hline(yintercept = color_below, linetype = "dashed", color = "black")

enter image description here

ggplot2 r
3 Answers

One option would be to add a column to your dataframe where using an ifelse assigns an NA to obs. between your threshold lines and map this new column on the color aes. These values will automatically be assigned the na.value of scale_color_discrete. To get rid of the NA entry in the legend I use the breaks argument and set the name for the color legend to Species so that it still gets merged with the shape legend.

library(ggplot2)

color_above <- mean(iris$Sepal.Width) + sd(iris$Sepal.Width)
color_below <- mean(iris$Sepal.Width) - sd(iris$Sepal.Width)

iris$color <- ifelse(iris$Sepal.Width > color_above | iris$Sepal.Width < color_below, as.character(iris$Species), NA_character_)

ggplot(data=iris, aes(x = Sepal.Length, y = Sepal.Width, color = color)) + 
  geom_point(aes(shape=Species)) +
  scale_color_discrete(breaks = unique(iris$Species), name = "Species") +
  xlab("Sepal Length") +
  ylab("Sepal Width")+
  geom_hline(yintercept = color_above, linetype = "dashed", color = "black") +
  geom_hline(yintercept = color_below, linetype = "dashed", color = "black")

user_129938610

You could add a new layer:

grey <- iris[iris$Sepal.Width < color_above & iris$Sepal.Width > color_below,]

ggplot(data=iris, aes(x = Sepal.Length, y = Sepal.Width)) + geom_point(aes(color=Species, shape=Species)) +
  xlab("Sepal Length") +  ylab("Sepal Width")+
  geom_hline(yintercept = color_above, linetype = "dashed", color = "black") +
  geom_hline(yintercept = color_below, linetype = "dashed", color = "black") +
  geom_point(data=grey,aes(x = Sepal.Length, y = Sepal.Width),color='grey')

enter image description here

user_135133280

We could also use gghighlight package: I think this made for such situations:

p +  gghighlight::gghighlight(Sepal.Width > 3.5 | Sepal.Width < 2.6)

enter image description here

user_133216470
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