Question

我有一个bioclim变量的砖文件，砖块是从四个30秒的瓷砖砖中合并而来的，所以它有点大。我想通过使用多边形作为边界来切割我的研究区域的砖文件。我该怎么办？否则，如果不能用砖做，我可以用光栅做吗？

提前致谢〜

马

Answer 1

如果要将砖块裁剪为较小的矩形，请查看extent()。如果您希望通过点击选择，也可以drawExtent()。

编辑：由于您使用了“剪切”和“掩码”这两个术语，我不确定我是否理解正确，但这里有两种方法可能有所帮助。你甚至可以同时使用它们。

# an example with dimensions: 77, 101, 3  (nrow, ncol, nlayers)
myGrid_Brick <- brick(system.file("external/rlogo.grd", package="raster"))

# a simple polygon within those dimensions
myTriangle_P <- Polygon(cbind(c(10, 80, 50, 10), c(10, 20, 65, 10)))
myTriangle_Ps <- Polygons(list(myTriangle_P), "fubar")
myTriangle_SP <- SpatialPolygons(list(myTriangle_Ps))
myTriangle_Ras <- rasterize(myTriangle_SP, myBrick)

# this will crop a brick to minimal rectangle that circumscribes the polygon
# extent(myCrop) is smaller than extent(myGrid) but no values are changed
myCrop_Brick <- crop(myGrid_Brick, myTriangle_SP)

# while this converts every coordinate that is NA in
# the mask to become NA in the returned brick
# while leaving the brick extent unchanged
myMask_Brick <- mask(myGrid_Brick, myTriangle_Ras)

如何用多边形切砖？

1 个答案: