code: ///////////////////////////////////////////////////////////////////////////////
  // 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.gene.tetrad.gene.algorithm.util;
  
  /**
   * Implements a space-efficient Lower Triangular Matrix of
   * elements of type <code>float</code>
   *
   * @author
   * <a href="http://www.eecs.tulane.edu/Saavedra" target="_TOP">Raul Saavedra</a>
   * (<a href="mailto:rsaavedr@ai.uwf.edu">rsaavedr@ai.uwf.edu</A>)
   */
  
  import java.io.FileNotFoundException;
  import java.io.IOException;
  
  public class LTMatrixF extends BasicLTMatrix {
      protected float[] A;
  
      /**
       * Creates a lower triangular matrix with <code>nrows</code> rows.
       */
      public LTMatrixF(String mname, int nrows) {
          super(mname, nrows);
      }
  
      /**
       * Creates a lower triangular matrix reading it from file
       * <code>fname</code>.
       */
      public LTMatrixF(String fname) throws FileNotFoundException, IOException {
          super(fname);
      }
  
      /**
       * Initializes the data structure used to hold the contents of the matrix
       */
      protected void initMatrixStorage() {
          this.A = new float[(this.n * (this.n + 1) / 2)];
      }
  
      /**
       * Casts double value x to float and assigns it to element (r,c) This
       * method checks that x can be converted to a float without causing
       * overflow.
       */
      public void setDoubleValue(int r, int c, double x) {
          setValue(r, c, x);
      }
  
      /**
       * Assigns double x to matrix element (r, c).  This method checks that x can
       * be converted to a float without causing overflow.
       */
      public void setValue(int r, int c, double x) {
          if ((x < MIN_FLOAT) || (x > MAX_FLOAT)) {
              throw new IllegalArgumentException(
                      "Double " + x + " cannot be stored as a float");
          }
          setValue(r, c, (float) x);
      }
  
      /**
       * Assigns float x to matrix element (r, c)
       */
      public void setValue(int r, int c, float x) {
          if (r < c) {
              upperTriangXcp(r, c);
          }
          if ((r >= this.n) || (c >= this.n) || (r < 0) || (c < 0)) {
              badIndexXcp(r, c);
          }
          this.A[(r * (r + 1) / 2 + c)] = x;
      }
  
      /**
       * Returns element (r,c) as a double
       */
      public double getDoubleValue(int r, int c) {
          if ((r >= this.n) || (c >= this.n) || (r < 0) || (c < 0)) {
              badIndexXcp(r, c);
          }
          return (double) (r >= c ? this.A[r * (r + 1) / 2 + c] : 0);
      }
  
      /**
       * Returns element (r,c)
       */
      public float getValue(int r, int c) {
          if ((r >= this.n) || (c >= this.n) || (r < 0) || (c < 0)) {
              badIndexXcp(r, c);
          }
          return (r >= c ? this.A[r * (r + 1) / 2 + c] : 0);
      }
  
      /**
       * Assign zero to all elements in the matrix
       */
      public void setAllValuesToZero() {
          for (int i = 0; i < this.A.length; i++) {
              A[i] = 0;
          }
      }
  
      private void upperTriangXcp(int r, int c) {
          throw new IllegalArgumentException("Trying to set a value in (" + r +
                  "," + c + ") -> " + "Upper Triangular region ");
      }
  
  }
  
  
  
  
  
  