scripts/builtin/intersect.dml

#-------------------------------------------------------------
#
# Licensed to the Apache Software Foundation (ASF) under one
# or more contributor license agreements.  See the NOTICE file
# distributed with this work for additional information
# regarding copyright ownership.  The ASF licenses this file
# to you under the Apache License, Version 2.0 (the
# "License"); you may not use this file except in compliance
# with the License.  You may obtain a copy of the License at
#
#   http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing,
# software distributed under the License is distributed on an
# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
# KIND, either express or implied.  See the License for the
# specific language governing permissions and limitations
# under the License.
#
#-------------------------------------------------------------

# Implements set intersection for numeric data
#
# INPUT:
# -----------------------------------------------------------------------------------
# X     matrix X, set A
# Y     matrix Y, set B
# -----------------------------------------------------------------------------------
#
# OUTPUT:
# ------------------------------------------------------------------------------------
# R     intersection matrix, set of intersecting items
# ------------------------------------------------------------------------------------

m_intersect = function(Matrix[Double] X, Matrix[Double] Y)
  return(Matrix[Double] R)
{
  X = unique(X);
  Y = unique(Y);
  combined = rbind(X, Y);

  combined = order(target=combined, by=1, decreasing=FALSE, index.return=FALSE);
  temp = combined[1:nrow(combined)-1,] == combined[2:nrow(combined),];
  mask = rbind(matrix(0,1,1), temp);

  R = removeEmpty(target = combined, margin = "rows", select = mask);
}