Filtering Function for Rico Schmitt: https://journal.medicine.berlinexchange.de/pub/nqjpou17/release/1
The purpose of this function: delete all duplicate values, as timepoint 1 and t2 cannot be connected unambivalently due to redundant encoding of id values.
Issue: duplicated() only solves for a logical with all duplicated values but does not return a logical that can be related to the original id column since it does not entail a TRUE for the value that is duplcated itself, as well.
EXAMPLE: In c( 1, 2, 2, 3) duplcated() returns: false, false, true, false. We want to delete all 2's in that column vector! I.e., we desire an output of false, true, true, false, in order to use that column vector to identify the rows in the data set, which are supposed to be deleted.
This function, simply called filtering(), served as a simple solution for the above problem that occured during the review / revision process.