ggplot-加热调色板

Question

i want a color scale like in the picture:

So from top to buttom we have:

a very bright yellow (white-ish), orange, red, black, blue, light blue to very bright blue (white-ish)

I want a value of 0 always to be displayed as "black". The smallest (negative) value should be that "extreme bright blue". The biggest value (postive) should be the "extreme bright yelllow".

Please note that the min and max are not equally distant from the origin 0.

Thats where i am:

library(ggplot2)
df <- data.frame(xDim = c(0, 1, 2, 0, 1, 2, 0, 1, 2), yDim = c(2, 2, 2, 1, 1, 1, 0, 0, 0), high = c(0, -1, 6, -3, 8, 5, -2, 7, 5))

ggplot(df, aes(xDim, yDim)) +
    geom_raster(aes(fill = high)) +
    scale_fill_gradient2(low = "blue", mid = "black", high = "red", midpoint = 0)

Answer 1

scale_fill_gradientn is most suited for this. You just need to get an appropriate vector of colors, then come up with a good range of values for those colors.

In your case, we could choose as colors:

col <- c('yellow', 'orange', 'red', 'black', 'blue', 'skyblue', 'white')

and as values:

val <- c(seq(min(df$high), 0, length.out = 4), seq(0, max(df$high), length.out = 4)[-1])

We need to use rescale according to the docs, so we do:

p <- ggplot(df, aes(xDim, yDim)) +
  geom_raster(aes(fill = high)) +
  scale_fill_gradientn(colours = col, values = scales::rescale(val))

cowplot::ggdraw() + cowplot::draw_plot(cowplot::get_legend(p))