lidR: Save LAS files from a clip_roi list

Question

I have clipped a point cloud with a shapefile containing multiple polygons, using clip_roi() function. The result is a list of LAS files. However, when I try to loop through the list and save each individual file, I get Error: Argument is not a LAS object. Here is the code:
las = readLAS("plot_a3.las", filter = "-drop_z_below 0")
polys = shapefile("plot_a_segments.shp")
clipped = clip_roi(las, polys)

for (i in range(lengths(clipped))) 
{
  file <-file.path('Plot_A', paste0('plot_a_', clipped[i], '.las'))
  writeLAS(clipped[i], file, index = FALSE)
}

How do I correctly save the output so that each clipped point cloud is saved as a separate LAS file?

JRR · Accepted Answer

clipped[i] returns a list with one element. You meant clipped[[i]] with double brackets. Also clipped[i] within paste0() is meaningless.
Actually your use case is already covered by the package. Assuming that your shapefile has an attribute PLOTID (replace with something else if needed)
ctg <- readLAScatalog("folder/plot_a3.las", filter = "-drop_z_below 0")
polys <- shapefile("folder/plot_a_segments.shp")

opt_output_files(ctg) <- "folder/plot_a_{PLOTID}"
new_ctg <- clip_roi(ctg, polys)

If you don't have any unique ID in the shapefile you can generate other filename patterns with {XCENTER}, {YCENTER}, {ID} and so on. See the documentation

lidR: Save LAS files from a clip_roi list

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