rasterize_terrain() with sfc shape

[wiesehahn]

In the documentation of rasterize_terrain() it says for shape argument: "It can also be an sfc to define a polygon in which to perform the interpolation."

In my understanding this means that I can pass a catalog and some region as sfc to get a dtm for that region. However, this seems not to work. E.g.:

# A single file LAScatalog using data provided with the package
LASfile <- system.file("extdata", "Megaplot.laz", package="lidR")
ctg = readLAScatalog(LASfile)

bbox <- st_bbox(ctg@data[1,])

dtm <- rasterize_terrain(ctg, res=1, shape= st_as_sfc(bbox))

outputs

Processing [==============================================================] 100% (1/1) eta:  0s
unable to find an inherited method for function ‘mosaic’ for signature ‘"SpatRaster", "missing"’Warning message:
An error occured during the automatic merge of 'catalog_apply'. Merging is impossible. A list has been returned. 

Is this an error or am I understanding it wrong?

[Jean-Romain]

Is this an error or am I understanding it wrong?

I think both !

First this is an error, it should work and actually it is related to the fact you are processing a single file. It is reproductible without shape and with any rasterize function

LASfile <- system.file("extdata", "Megaplot.laz", package="lidR")
ctg = readLAScatalog(LASfile)
chm = rasterize_canopy(ctg, 1, p2r())

Second, your example seems useless to me. Please exaplain what you have in mind when using shape= st_as_sfc(bbox) so I can see if something can be inproved in the documentation. Thank.

[Jean-Romain]

Fixed

[wiesehahn]

Ok, so my initial intention was to skip the step to clip the catalog (las <- clip_roi(ctg, bbox)), but instead definde the area of the requested dtm inside rasterize_terrain()

e.g.

ctg <- readLAScatalog(folder)

# get area as bbox from one of the las files
bbox <- st_bbox(ctg@data[1,])

dtm <- rasterize_terrain(ctg, res=1, shape= st_as_sfc(bbox))

this results in

Processing [-------------------------------]   0% (1/49588) eta:  8d
#> Error: subscript out of bounds

[Jean-Romain]

Ok, so my initial intention was to skip the step to clip the catalog (las <- clip_roi(ctg, bbox))

That makes sense and looks like a perfectly valid use of the argument shape if the shape is smaller than the tiles or if the shape is complex. But if the shape is the bounding box of the single tile it is equivalent as not providing anything. You can also do

ctg$processed = FALSE
ctg$processed[1] = TRUE
dtm <- rasterize_terrain(ctg)

Error: subscript out of bounds

Fixed. Especially it did not behave as expected. Thank you for reporting