r - 水平图颜色键 - 范围和极值

Question

是否可以在 R 中创建如下所示的颜色键？ (这个来自软件Grid Analysis and Display System - Grads)。



我无法在 R 中重现两个功能:

该序列是非线性的，但显示为

大于 200 的值是灰色/小于 0 的值是白色

我正在使用来自 rastervis 的 levelplot，它使用点阵 levelplot 绘制栅格:

require(raster)
require(rasterVis)

set.seed(200)

X = seq(-40,0,by=1)
Y = seq(-60,-40,by=1)
grid = expand.grid(list(X=X,Y=Y))
Z = rnorm(nrow(grid),mean=10,sd=100)

data = data.frame(grid,Z)
r = rasterFromXYZ(data)
mapTheme <- rasterTheme(region=c('#EEF7FA','#D6F8F7',"#BEDAFF",'#5DA4FF',"#0000FF","#D4F9E2","#00FF7F","#008000","#FFFF00","#FFD27F", "#FFB732"    ,"#EE7600",
                                 "#D53E4F","#FF6A6A"))  
my.at = c(0,1,5,10,15,20,25,30,40,50,75,100,150,200)
myColorkey <- list(at=my.at,
                   space="bottom",
                   labels=list(at=my.at))
p=levelplot(r, par.settings=mapTheme,at = my.at, colorkey=myColorkey,margin=F)
print(p)

结果:



如您所见，小于 0 和大于 200 的值都是白色的，我不知道如何设置大于或小于某个值的值以显示为特定颜色。 Morover，如何使颜色键中连续粗标记之间的空间具有相同的大小，尽管间隔不相同？

Answer 1

这是用于非线性序列的相同大小间隔的解决方法:

library(raster)
library(rasterVis)

set.seed(200)
X = seq(-40,0,by=1)
Y = seq(-60,-40,by=1)
grid = expand.grid(list(X=X,Y=Y))
Z = rnorm(nrow(grid),mean=10,sd=100)

data = data.frame(grid,Z)
r = rasterFromXYZ(data)
mapTheme <- rasterTheme(region=c('#EEF7FA','#D6F8F7',"#BEDAFF",'#5DA4FF',"#0000FF","#D4F9E2","#00FF7F",
                                 "#008000","#FFFF00","#FFD27F", "#FFB732" ,"#EE7600", "#D53E4F","#FF6A6A"))  

my.at=c(0,1,5,10,15,20,25,30,40,50,75,100,150,200)
my.brks=seq(0, 200, by=15)

myColorkey <- list(at=my.brks, labels=list(at=my.brks, labels=my.at), space="bottom")
p=levelplot(r, par.settings=mapTheme, at=my.at, colorkey=myColorkey, margin=F)
print(p)

对于小于 0 且大于 200 的值，这可能是一个解决方案:

library(raster)
library(rasterVis)

set.seed(200)
X = seq(-40,0,by=1)
Y = seq(-60,-40,by=1)
grid = expand.grid(list(X=X,Y=Y))
Z = rnorm(nrow(grid),mean=10,sd=100)

data = data.frame(grid,Z)
r = rasterFromXYZ(data)
mapTheme <- rasterTheme(region=c('white','#EEF7FA','#D6F8F7',"#BEDAFF",'#5DA4FF',"#0000FF","#D4F9E2","#00FF7F",
                                 "#008000","#FFFF00","#FFD27F", "#FFB732" ,"#EE7600", "#D53E4F","#FF6A6A", "gray"))  
max(values(r))
min(values(r))

my.at=c(min(values(r)), 0,1,5,10,15,20,25,30,40,50,75,100,150,200, max(values(r)))
my.brks=seq(0, 200, by=13)

myColorkey <- list(at=my.brks, labels=list(at=my.brks, labels=c(-276,0,1,5,10,15,20,25,30,40,50,75,100,150,200, 388)), space="bottom")
p=levelplot(r, par.settings=mapTheme, at=my.at, colorkey=myColorkey, margin=F)
print(p)

你的颜色没有从浅到深。您可以使用 RColorBrewer 包来解决这个问题。

library(RColorBrewer)
reds = brewer.pal(5, "YlOrRd")
greens = brewer.pal(3, "Greens")
blues = brewer.pal(5, "Blues")
mapTheme <- rasterTheme(region=c('white', blues, greens, reds, "gray"))