Function to Sample Rows from a Data Frame Excluding the ID Values from Another Sample Data Frame

df_sample_exIDs.r

# This function assumes that you're going to input ID1.name and ID2.name as strings.
df.sample.exIDs = function(main.df, sample1.df, n, ID1.name, ID2.name) {
  main.ID1.notin.ID2 = main.df[!main.df[,ID1.name] %in% sample1.df[,ID2.name],]
  sample2.df = main.ID1.notin.ID2[sample(nrow(main.ID1.notin.ID2), size=n),]
  return(sample2.df)
}