如何设置阶梯色区域? [英] How to set up step color regions?

问题描述

对于levelplot/spplot，我们可以使用at定义颜色区域范围(最小，最大，间隔).我的问题是:如何将红色用于大于29.5的值?

With levelplot/spplot we can use at to define the color region range (min, max, interval). My question is: how can I use red for values greater than 29.5?

这是我的示例NCDF文件->

This is my sample NCDF file --> download here

 library (raster)
 r <- brick('bali.nc', varname='TEMPERATURE', level=1)

 library(rasterVis)
 jet <- colorRampPalette(
   c('#00007F', 'blue', '#007FFF', 'cyan', 'yellow', '#FF7F00', 'red', '#7F0000')
 )

 # First Figure - without at
 levelplot(r, layer=1, margin=F, contour=F, col.regions=jet)

 # Second Figure - with at
 levelplot(r, layer=1, margin=F, contour=F, col.regions=jet, at=seq(27.5, 29.5, 0.1))

推荐答案

您必须在中断值向量中包括最大值，并相应地定义调色板:

You have to include the maximum value in the vector of break values, and define the palette accordingly:

rMax <- cellStats(r, max)
myAt <- c(seq(27.5, 29.5, 0.1), rMax[1])
myPal <- jet(length(myAt) - 1)

levelplot(r, layer = 1, margin = FALSE,
          at = myAt,
          par.settings = rasterTheme(myPal))

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