Plot 光栅，具有连续调色板，白色为零（R 基）

Question

As much as I looked at other questions I couldn't solve my problem (I'm new in R). I simply need to plot a raster where the minimum value (let's say color red) goes to zero (white) and from zero to maximum (color blue) continuously. I would like to create that color palette independently if the data is symmetrically distributed in negative and positive values.

Let's say I have a raster with this values:

library(raster)
values <- c(seq(-2000,0,by=1),seq(1,499,by=1))
values <- sample(values)

r <- raster(ncol=50,nrow=50)
r <- setValues(r,values)

plot(r)

If this has already been resolved in another question, I would appreciate any information. Thank you

Answer 1

So, you can use RColorBrewer or colorRampPalette to achieve this (or a combination of both) and by setting breaks .

library(raster)
library(RColorBrewer)

breakpoints <- c(-2000, seq(0, 500, 55.6))
colors <- c("red", RColorBrewer::brewer.pal(9, "Blues"))
plot(r, breaks = breakpoints, col = colors)

Output

You can also do something similar with colorRampPalette by setting two unique colors. Then, in parenthesis, define how many colors on the gradient you want.

colors <- c("red", colorRampPalette(c("steelblue1", "steelblue4"))(9))

You can also use these both in conjunction with one another.

colors <- c("red", colorRampPalette(RColorBrewer::brewer.pal(9, "Blues"))(11))

If you want red also continuous, then you could create a gradient for both.

breakpoints <- c(seq(-2000, -1, 222), seq(0, 500, 55.6))
colors <- c(RColorBrewer::brewer.pal(9, "Reds"), RColorBrewer::brewer.pal(9, "Blues"))
plot(r, breaks = breakpoints, col = colors)

Output