9.2 Example Using the Vector Classes

FILENAME: example1.cpp

Program:

/*

 * Example program using class RWMathVec<double>
 * to do simple statistics with double precision vectors.
 */

// Include the RWMathVec<double> class header file.
#include <rw/math/mathvec.h>

#include <iostream.h>

main()
{
   // Declare the double precision vector V:
   RWMathVec<double> V;

   // Read the vector from standard input:
   cin >> V;

   /*
    * Output the length of the vector.
    * This illustrates the use of an RWMathVec<double>
    * member function.
    */

   cout << "The length of the vector is:\t"
        << V.length() << "\n";

   /*
    * Calculate the mean of the vector.
    * This illustrates the use
    * of the global function mean().
    */
   double avg = mean(V);

   cout << "The mean of the vector is:\t" << avg << "\n";

   /*
    * Find the index of the maximum element of
    * the vector and output the value.
    */
   int maxV = maxIndex(V);
   cout << "The maximum value of the vector is:\t"
     << V(maxV) << "\n";

   // Output the variance of the vector:

   cout << "The variance of the vector is:\t"
        << variance(V) << "\n";

   /*
    * Here is how to demean and normalize a 
    * vector and print out the result.
    */
   V -= mean(V);                  // Remove the mean
   maxV = maxIndex(V);            // Max element
   if ( V(maxV) != 0) {
      V /= fabs(V(maxV));
      cout << "The normalized demeaned vector is:\n" << V;
   }
}

Sample Input:

[ 1.33  -23.7   -.23  16.46   9.5 
  3.14   11.3  -1.    24.23. 12.3 ]

Sample Output:

The length of the vector is: 10
The mean of the vector is: 5.333
The maximum value of the vector is: 24.23
The variance of the vector is:  151.721701
The normalized demeaned vector is:
[
-0.211833 -1.536381 -0.294385 0.588824 0.220511
-0.11605 0.315764 -0.335133 1 0.3686831
]