使用levelplot在rasterVis中绘制分类数据时更改背景颜色(Change background colour when plotting categorical data in rasterVis using levelplot)

 我有一个分类数据(lulc)用于土地使用土地覆盖有6个类别。 我试图在rasterVis使用levelplot绘制这些数据 
 
l<-as.factor(lulc)
rat <- levels(l)[[1]]
rat[["landcover"]] <- c("Agriculture", "Bare land", "Built-up", "Vegetation","Water","Wetland")
levels(lulc) <- rat
levelplot(lulc, col.regions=c("yellow","cyan","pink","green","lightblue","orange"), xlab="", ylab="")
 
 但研究区域是沿海地区。 因此，我希望将NA显示为用“浅蓝色”代表的海洋。 我尝试了panel.background="lightblue" ，但它没有改变剧情中的任何内容。 我得到的是以下;  
 
 但我想要跟随;  

I have a categorical data (lulc) for a land use land cover having 6 classes. I am trying to plot this data using levelplot in rasterVis
 
l<-as.factor(lulc)
rat <- levels(l)[[1]]
rat[["landcover"]] <- c("Agriculture", "Bare land", "Built-up", "Vegetation","Water","Wetland")
levels(lulc) <- rat
levelplot(lulc, col.regions=c("yellow","cyan","pink","green","lightblue","orange"), xlab="", ylab="")
 
But the study area is coastal. Hence I want to show NAs as ocean represented with "lightblue". I tried panel.background="lightblue", but it does not change anything in the plot. What I get is following; 
 
But I want as following; 

原文：https://stackoverflow.com/questions/35941573