问计算保护区多边形与预测的最大栖息地适宜性的重叠

EN

zonal.stats(x, y, stats = c("min", "mean", "max"))
#x = Polygon object of class SpatialPolygonsDataFrame
#y = rasterLayer object of class raster

library(spatialEco)    
library(raster)
library(sp)                                                                          

# here the fxn will calculate the percentage of cells >= 0.5
# percent x >= p function
pct <- function(x, p=0.50, na.rm = FALSE) {
  if ( length(x[x >= p]) < 1 )  return(0) 
  if ( length(x[x >= p]) == length(x) ) return(1) 
  else return( length(x[x >= p]) / length(x) ) 
}

# create some example data
p <- raster(nrow=10, ncol=10)
p[] <- runif(ncell(p)) * 10
p <- rasterToPolygons(p, fun=function(x){x > 9})
r <- raster(nrow=100, ncol=100)
r[] <- runif(ncell(r)) 
plot(r)
plot(p, add=TRUE, lwd=4) 

# run zonal statistics using pct functions  
z.pct <- zonal.stats(x=p, y=r, stats = "pct")
z.pct

#Alternatively, reclassify the raster based on a threshold
r.c<-reclassify(r, c(-Inf, 0.5, 0, 0.5, Inf, 1)) #all values >0.5 reclassified to 1
plot(r.c)
plot(p, add=TRUE, lwd=4) #add poly to the plot

# run zonal stats and calculate sum of cells in each poly
z.sum <- zonal.stats(x=p, y=r.c, stats = "sum")
z.sum