问在viridis或RColorBrewer中设置颜色范围的参考值

EN

library(ggplot2)
library(RColorBrewer)

# data
set.seed(1)
df <- expand.grid(x = 0:5, y = 0:5)
df$z <- runif(nrow(df))

# plot
ggplot(df, aes(x, y, fill = z)) + geom_raster() +
  scale_fill_distiller( palette="RdBu", guide = "colorbar")

# plot using viridis
library(viridis)

ggplot(df, aes(x, y, fill = z)) + geom_raster() +
  scale_fill_viridis()

ggplot(df, aes(x, y, fill = z)) + geom_raster() +
  scale_fill_gradient2( low = "#2166ac", mid = "#f7f7f7", high = "#b2182b", midpoint = 0.2, 
                        space = "Lab", na.value = "grey50", guide = "colourbar")