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# Implements set intersection for numeric data  


# INPUT PARAMETERS:
# ---------------------------------------------------------------------------------------------
# NAME            TYPE    DEFAULT     MEANING
# ---------------------------------------------------------------------------------------------
# X               Double  ---         matrix X, set A
# Y               Double  ---         matrix Y, set B
# ---------------------------------------------------------------------------------------------
 
# Output(s)
# ---------------------------------------------------------------------------------------------
# NAME            TYPE    DEFAULT      MEANING
# ---------------------------------------------------------------------------------------------
# R               Double  ---         intersection matrix, set of intersecting items

m_intersect = function(Matrix[Double] X, Matrix[Double] Y)
  return(Matrix[Double] R)
{
  # compute indicator vector of intersection output
  X = (table(X, 1) != 0) 
  Y = (table(Y, 1) != 0)
  n = min(nrow(X), nrow(Y))
  I = X[1:n,] * Y[1:n,]

  # reconstruct integer values and create output
  R = removeEmpty(target=seq(1,n), margin="rows", select=I)
}