题
我有一个bioclim变量的砖块文件,该砖块是由四个30秒的砖块合并而成的,所以它有点大。我想通过使用多边形作为边界进行切割来获取我的研究区域的砖块文件。我应该怎么办?否则,如果不可能用砖来做,我可以用光栅来做吗?
先谢谢啦~
马可
解决方案
查看 extent()
如果你想将砖块裁剪成更小的矩形。还 drawExtent()
如果您想通过点击进行选择。
编辑:由于您使用了术语“剪切”和“蒙版”,我不确定我是否理解正确,但这里有两种方法可能会有所帮助。您甚至可以同时使用两者。
# 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)
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