scales_fill_continuous 不起作用（ggplot2）

Question

I have a data:

df_1 <- data.frame(
  x = replicate(
    n = 2, expr = rnorm(n = 3000, mean = 100, sd = 10)
  ), 
  y = sample(x = 1:3, size = 3000, replace = TRUE)
)

And the follow function:

library(tidyverse)

ggplot(data = df_1, mapping = aes(x = x.1, fill = x.1)) + 
  geom_histogram(color = 'black', bins = 100) + 
  scale_fill_continuous(low = 'blue', high = 'red') + 
  theme_dark()

scale_fill_continuous doesn't work. The graph is black and gray.

Tks.

Answer 1

The problem, I think, is that there are nrow(df_1) values for fill, but only 100 are needed. This could be solved by pre-calculating the bin positions and counts and plotting with geom_col , but a neater solution is to use stat . stat is supposed to be for computed variables (eg stat(count) - see ?geom_histogram ) but we can give it the vector 1:nbin and it works.

df_1 <- data.frame(
  x = replicate(n = 2, expr = rnorm(n = 3000, mean = 100, sd = 10)), 
  y = sample(x = 1:3, size = 3000, replace = TRUE)
)

library(tidyverse)
nbins <- 100
ggplot(data = df_1, mapping = aes(x = x.1, fill = stat(1:nbins))) + 
  geom_histogram(bins = nbins) + 
  scale_fill_continuous(low = "red", high = "blue")

^{Created on 2020-01-19 by the reprex package (v0.3.0)}

Answer 2

The aes fill should be stat(count) rather than x.1

ggplot(data = df_1, mapping = aes(x = x.1, fill = stat(count))) + 
  geom_histogram(color = 'black', bins = 100) + 
  scale_fill_continuous(type = "gradient", low = "blue", high = "red") +
  theme_dark()