如何将栅格数据框与shapefile结合以创建物种丰富度地图？

Question

我想在shapefile上绘制栅格图/数据框，但根据编写代码的方式，我会不断遇到各种错误。

我尝试对已完成的对象（地图+划痕图）使用+，我尝试将代码加在一起并将两者作为数据绘制，但这没用：

我已经尝试了以下以及其他方法...

谢谢您的帮助/指导。

critmapped<-ggplot(df, aes(x, y, fill = layer)) + 
geom_raster() +
scale_fill_viridis_c(na.value = "white") +
labs(fill = "Count") + 
theme_minimal() + ggplot() + geom_path(data = land_df, aes(x = long, y = lat, group = group), color = 'black', fill = 'green')

#Error: Don't know how to add ggplot() to a plot

critmapped+landmap2
#Error: Don't know how to add landmap2 to a plot

#The shapefile code

  require(rgdal)
  land <- readOGR(dsn = "C:/Users/tjef631/Desktop/R Stats/Data/NE_10m_full", 
  layer = "ne_10m_land")
  land_df<-fortify(land)
  names(land_df)
  landmap<-ggplot() + geom_path(data = land_df, aes(x = long, y = lat, group 
  = group),
            color = 'black', fill = 'green')
landmap


#the raster/dataframe code

  critmapped<-ggplot(df, aes(x, y, fill = layer)) + 
  geom_raster() +
  scale_fill_viridis_c(na.value = "white") +
  labs(fill = "Count") + 
  theme_minimal()

  critmapped