具有分类数据的栅格图的图例 [英] Legend of a raster map with categorical data

问题描述

我想绘制一个包含4个不同值的栅格（ 1 ）描述类别的分类文字图例，例如 2 ，但带有彩色框：

I would like to plot a raster containing 4 different values (1) with a categorical text legend describing the categories such as 2 but with colour boxes:

我尝试过使用图例：

legend( 1,-20,legend = c("land","ocean/lake", "rivers","water bodies"))

但我不知道如何将一个值与显示的颜色相关联。有没有办法检索plot显示的颜色并在图例中使用？

but I don't know how to associate one value to the displayed color. Is there a way to retrieve the colour displayed with 'plot' and to use it in the legend?

推荐答案

rasterVis 包中包含一个 levelplot（）的栅格方法，绘制了分类变量，并生成了一个适当的图例：

The rasterVis package includes a Raster method for levelplot(), which plots categorical variables, and produces an appropriate legend:

library(raster)
library(rasterVis)

## Example data
r <- raster(ncol=4, nrow=2)
r[] <- sample(1:4, size=ncell(r), replace=TRUE)
r <- as.factor(r)

## Add a landcover column to the Raster Attribute Table
rat <- levels(r)[[1]]
rat[["landcover"]] <- c("land","ocean/lake", "rivers","water bodies")
levels(r) <- rat

## Plot
levelplot(r, col.regions=rev(terrain.colors(4)), xlab="", ylab="")

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