03_select-ref-samples.R

################################################################################
## Task: Select reference samples for soil refence analyses by using
##   Kennard-Stones
##   sampling algorithm on preprocessed spectra in PCA space
################################################################################

# Load packages
library("tidyverse")
library("simplerspec")

# Read spectral tibble from Rds file
spc_tbl <- read_rds(path = "out/files/spc_tbl.Rds")

ref_samples_2pc <- select_ref_spc(
  spc_tbl = spc_tbl,
  ratio_ref = 0.15, # ratio of desired reference samples to total sample number
  pc = 2, # Number of principal components considered
  print = TRUE) # print plot of PCA space

# Test 6 PCs
ref_samples_6pc <- select_ref_spc(
  spc_tbl = spc_tbl,
  ratio_ref = 0.15, # ratio of desired reference samples to total sample number
  pc = 6, # Number of principal components considered
  print = TRUE)

## Compare if different samples have been chosen...
ref_samples_2pc$spc_ref$sample_id
ref_samples_6pc$spc_ref$sample_id