text: ///////////////////////////////////////////////////////////////////////////////
  // For information as to what this class does, see the Javadoc, below.       //
  // Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006,       //
  // 2007, 2008, 2009, 2010, 2014, 2015 by Peter Spirtes, Richard Scheines, Joseph   //
  // Ramsey, and Clark Glymour.                                                //
  //                                                                           //
  // This program is free software; you can redistribute it and/or modify      //
  // it under the terms of the GNU General Public License as published by      //
  // the Free Software Foundation; either version 2 of the License, or         //
  // (at your option) any later version.                                       //
  //                                                                           //
  // This program is distributed in the hope that it will be useful,           //
  // but WITHOUT ANY WARRANTY; without even the implied warranty of            //
  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the             //
  // GNU General Public License for more details.                              //
  //                                                                           //
  // You should have received a copy of the GNU General Public License         //
  // along with this program; if not, write to the Free Software               //
  // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA //
  ///////////////////////////////////////////////////////////////////////////////
  
  package edu.cmu.tetrad.util;
  
  import cern.colt.matrix.DoubleFactory2D;
  import cern.colt.matrix.DoubleMatrix2D;
  import cern.colt.matrix.impl.DenseDoubleMatrix1D;
  import cern.colt.matrix.impl.DenseDoubleMatrix2D;
  import cern.colt.matrix.linalg.Algebra;
  
  /**
   * Some algebra methods.
   */
  public class TetradAlgebra {
  
      public static TetradMatrix multOuter(TetradVector v1, TetradVector v2) {
          DoubleMatrix2D m = new Algebra().multOuter(new DenseDoubleMatrix1D(v1.toArray()),
                  new DenseDoubleMatrix1D(v2.toArray()), null);
          return new TetradMatrix(m.toArray());
      }
  
      public static TetradMatrix solve(TetradMatrix a, TetradMatrix b) {
          DoubleMatrix2D _a = new DenseDoubleMatrix2D(a.toArray());
          DoubleMatrix2D _b = new DenseDoubleMatrix2D(b.toArray());
          return new TetradMatrix(new Algebra().solve(_a, _b).toArray());
      }
  
      public static TetradMatrix identity(int rows) {
          return new TetradMatrix(DoubleFactory2D.dense.identity(rows).toArray());
      }
  }
  
  
  
  