Calculate metrics LiDR

Question

Would it be possible to calculate a density metric in height intervals as in FUSION or Lastools? e.g number of all returns between 0.2 and 3 meters/number of total returns in 1 meters cell. I'm trying to compute using the function of the package stdmetrics_z(z) but I had an error with fast_table

myMetrics2 = function (z) { 
  n = length(z)
  zmax = max(z)
  zmean = mean(z)
  if (zmax <= 0) {
    d = rep(0, 9)
  }
  else {
    breaks = seq(0.2, 25, 2.8)
    d = findInterval(z, breaks)
    d = fast_table(d, 10)
    d = d/sum(d) * 100
    d = cumsum(d)[1:9]
    d = as.list(d)
  }
  names(d) = paste0("zpcum", 1:9)
  metrics = c( d)
  return(metrics)
}

metric2=grid_metrics(ctgn.i, ~myMetrics2(z, res=1)
#> Processing [=========================================] 100% (1/1) eta:  0s
#> Error: could not find function "fast_table"

Answer 1

I guess you are trying to write a function like this. But it is hard to say because your code example is not related at all to your text description. I based this answer on your text description.

f = function(z) {
  n02.3 = sum(z >= 0.2 & z <= 3)
  n = length(z)
  return(list(ratio = n02.3/n))
}

metric2 = grid_metrics(ctgn.i, ~f(z), res = 1)