With the excellent lidR package we can filter at C++ level when using readLAS()
, e.g. with the following syntax
lidar = readLAS(LASfile, filter="-keep_first")
or when the pointcloud is already loaded at the R level, where above filter would translate to:
lidar_first = filter_poi(lidar, ReturnNumber == 1L)
Now I am wondering: What is the equivalent to keep_last
?
It would be nice having a full list of attributes I could filter on. The doc elaborates on (LAStools/C++) options at the readLAS
function (respectively one can list these with readLAS(filter = "-help")
), but I haven't found a list of the R equivalents.
Best Answer
With a little trial and error, I found that this works:
The list of potential select attributes for
readLAS
in the documentation gave me the hint that there might be a variableNumberOfReturns
available (there it is called r - number of returns). However I haven't found any explicit hints on that anywhere.A comprehensive list of filter options for
readLAS()
/opt_filter()
can be found by runningreadLAS(filter = "-help")