Question

如何找到两个栅格对象的交集？

e1 = extent(0, 10, 0, 10) #xmin, xmax, ymin, ymax
s1 = raster(e1, nrows=10, ncols=10, crs=CRS('+proj=longlat +datum=WGS84 +ellps=WGS84 +towgs84=0,0,0'))

e2 = extent(0, 12, 3, 10) #xmin, xmax, ymin, ymax
s2 = raster(e2, nrows=10, ncols=10, crs=CRS('+proj=longlat +datum=WGS84 +ellps=WGS84 +towgs84=0,0,0'))

e3 = extent(24, 50, 40, 50) #xmin, xmax, ymin, ymax
s3 = raster(e3, nrows=10, ncols=10, crs=CRS('+proj=longlat +datum=WGS84 +ellps=WGS84 +towgs84=0,0,0'))

Answer 1

以下代码应该有效。它还处理了一些奇怪的错误。

library(raster)
library(sp)

# define rasters      
e1 = extent(0, 10, 0, 10) #xmin, xmax, ymin, ymax
s1 = raster(e1, nrows=10, ncols=10, crs=CRS('+proj=longlat +datum=WGS84 +ellps=WGS84 +towgs84=0,0,0'))

e2 = extent(0, 12, 3, 10) #xmin, xmax, ymin, ymax
s2 = raster(e2, nrows=10, ncols=10, crs=CRS('+proj=longlat +datum=WGS84 +ellps=WGS84 +towgs84=0,0,0'))

e3 = extent(24, 50, 40, 50) #xmin, xmax, ymin, ymax
s3 = raster(e3, nrows=10, ncols=10, crs=CRS('+proj=longlat +datum=WGS84 +ellps=WGS84 +towgs84=0,0,0'))


test_intersection <- function(a,b){
   #reads in two rasters and tests for overlap T or F
   # if returns TRUE then there is overlap
   if(class(a)!='Extent'){ a  = extent(a)}
   if(class(b)!='Extent'){ a  = extent(b)}
   !class(try(intersect(a,b),T ))=='try-error'}





# Test function
intersect(e1,e2)library(raster)
library(sp)

# define rasters      
e1 = extent(0, 10, 0, 10) #xmin, xmax, ymin, ymax
s1 = raster(e1, nrows=10, ncols=10, crs=CRS('+proj=longlat +datum=WGS84 +ellps=WGS84 +towgs84=0,0,0'))

e2 = extent(0, 12, 3, 10) #xmin, xmax, ymin, ymax
s2 = raster(e2, nrows=10, ncols=10, crs=CRS('+proj=longlat +datum=WGS84 +ellps=WGS84 +towgs84=0,0,0'))

e3 = extent(24, 50, 40, 50) #xmin, xmax, ymin, ymax
s3 = raster(e3, nrows=10, ncols=10, crs=CRS('+proj=longlat +datum=WGS84 +ellps=WGS84 +towgs84=0,0,0'))


test_intersection <- function(a,b){
  #reads in two rasters and tests for overlap T or F
  # if returns TRUE then there is overlap
  # try error is included b/c errors has come up with other test data
  !(class(try(intersect(a,b),T ))=='try-error' | is.null(intersect(a,b)))
}

# Test function
intersect(e1,e2)
test_intersection(e1,e2)

intersect(e1,e3)
test_intersection(e1,e3)


test_intersection(e1,e2)

intersect(e1,e3)
test_intersection(e1,e3)

R - 测试栅格是否相交

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