Question

使用“蒙版”功能根据多边形切割光栅后：

ras <- mask(ras0, polygon)

我想用ggplot呈现栅格（下面的链接）。但是，我的切割光栅外部的“NA”值存在问题。

https://depots.univ-perp.fr/get?k=9sh9zKXDpRTkVQslvJk

我在“scale_fill_manual”中添加选项na.value =“transparent”，将NA值透明地放在我的地图上，但NA的图例始终保留！

如何在图例中删除文字“NA”和灰色对应的方框？
当使用“掩码”功能或使用“Writeraster”注册时，是否有解决方法可以去除NA值，以避免在使用ggplot显示时出现此问题？

以下是用于显示地图的程序：

library(raster) 
ras<-raster("ras.tif")

# map
gplot(ras)+
  geom_tile(aes(fill=factor(value, labels=c("A", "B", "C", "D", "E", "F","G"))))+
  scale_fill_manual(values = c("red", "#22751a", "#48c665", "#d3d532", "#d78d0d", "#f6e600","#65d6ef"),
                    name= "Legend", na.value="transparent")+
  coord_cartesian(xlim = c(-7, 12),ylim = c(32, 38)) +
#bg
theme(panel.background = element_rect(colour = "black", fill="lightblue"))

提前谢谢

Answer 1

似乎scale_fill_manual在使用因素时显示NA值。定义您真正想要展示的因素的方法是使用其他参数breaks和labels以及对应的向量。如果我使用你的代码，那就是：

# Vector of correspondence
cols <- c("A" = "red", "B" = "#22751a", "C" = "#48c665",
          "D" = "#d3d532", "E" = "#d78d0d", "F" = "#f6e600","G" = "#65d6ef")

# plot
gplot(ras) +
geom_tile(aes(fill=factor(value, labels=c("A", "B", "C", "D", "E", "F","G"))))+
  scale_fill_manual(values = cols,
                    breaks = c("A", "B", "C", "D", "E", "F","G"),
                    labels = c("A", "B", "C", "D", "E", "F","G"),
                    name= "Legend") +
  coord_cartesian(xlim = c(-7, 12),ylim = c(32, 38)) +
theme(panel.background = element_rect(colour = "black", fill="lightblue"))

但是，您可以以另一种方式使用它，同时将光栅的值（作为字符）直接归因于特定颜色然后命名（我必须添加新颜色，因为您的栅格中有8个级别）：

# Vector of correspondence
cols.nb <- c("0" = "blue", "1" = "red", "2" = "#22751a", "3" = "#48c665",
          "4" = "#d3d532", "5" = "#d78d0d", "6" = "#f6e600", 
          "7" = "#65d6ef")
# Plot
gplot(ras) +
geom_tile(aes(fill = as.character(value))) +
  scale_fill_manual(values = cols.nb,
                    breaks = 0:7,
                    labels = c("A", "B", "C", "D", "E", "F","G","H"),
                    name = "Legend") +
  coord_cartesian(xlim = c(-7, 12),ylim = c(32, 38)) +
theme(panel.background = element_rect(colour = "black", fill="lightblue"))

ggplot如何在使用“mask”剪切后显示没有NA值的栅格？

1 个答案: