Calculating Rumple_Index for clipped Inventory Plot LAS files

Question

I have successfully implemented the Rumple_Index example provided in the LidR book. I am now trying to calculate the same Rumple_Index for my forest field plots. I am trying to integrate the Rumple_Index function used for the landscape analysis at my plot scale. I am using code to do this that I have used to calculate Zmetrics for the plots already (substituting the rumple_Index function).

The error I am getting now is:

Error in UseMethod("readLAS", files) : 
  no applicable method for 'readLAS' applied to an object of class "c('cluster', 'multiprocess', 'future', 'function')"
Called from: readLAS(cluster)

This is a simplified version of the code I am trying to run.

rumple_index_surface = function(cluster, res)
{
  las = readLAS(cluster)
  if (is.empty(las)) return(NULL)
  las <- filter_surfacepoints(las, 1)  
  rumple <- grid_metrics(las, ~rumple_index(X,Y,Z), res)
  bbox <- raster::extent(cluster)
  rumple <- raster::crop(rumple, bbox)
  return(rumple)
}

LASlist <- list.files(path to clipped LAZ plots) # create a list of the LAZ files to cycle through

getMetrics <- data.frame() 

for ( i in LASlist) {
  lidar = readLAS(i)
  getMetrics <- rbind(getMetrics, cloud_metrics(lidar, ~rumple_index_surface(cluster, res = 25)))
}

How can my code be improved?

Answer 1

You can simply compute the rumple index from the XYZ coordinates of your plots

las <- readLAS(i)
las <- filter_surfacepoints(las, 1)  
ri  <- rumple_index(las$X,las$Y,las$Z)

or using a CHM

las <- readLAS(i)
chm <- grid_canopy(las, 1, p2r())
ri  <- rumple_index(chm)