core: vertical_segment: Consolidate 'Eigen::Map' creation as methods.

sources/core/vertical_segment.cpp

@@ -130,13 +130,7 @@ void vertical_segment::get(int i, vec& yl, vec& yu) const
 
 vec vertical_segment::get(int i) const
 {
-    // Omit the confidence interval data.
-    auto relevant_rows = _parameters.dimX() + _parameters.dimY();
-    auto matrix =
-        Map<MatrixXd, 0, OuterStride<> >(_data.get(), relevant_rows, size(),
-                                         OuterStride<>(column_number()));
-
-    return matrix.col(i);
+    return data_view().col(i);
 }
 
 void vertical_segment::set(int i, const vec& x)
@@ -146,8 +140,7 @@ void vertical_segment::set(int i, const vec& x)
    if(x.size() == column_number()
       || x.size() == _parameters.dimX() + _parameters.dimY())
    {
-       auto matrix = matrix_view();
-       auto row = matrix.row(i);
+       auto row = matrix_view().row(i);
        row.head(x.size()) = x;
    } else {
       std::cerr << "<<ERROR>> Passing an incorrect element to vertical_segment::set" << std::endl;

sources/core/vertical_segment.h

@@ -113,13 +113,24 @@ class vertical_segment : public data
           return _parameters.dimX() + 3 * _parameters.dimY();
       }
 
-      // Return a matrix view of this data.
+      // Return a matrix view of the data: all the Xi and Yi followed by
+      // confidence interval data (lower and upper bound of the Yi).  Thus,
+      // it has (dimX + 3 * dimY) columns and SIZE rows.
       Eigen::Map<Eigen::MatrixXd> matrix_view() const
       {
           return Eigen::Map<Eigen::MatrixXd>(_data.get(), size(),
                                              column_number());
       }
 
+      // Return a matrix view of DATA that excludes confidence interval data.
+      // It has (dimX + dimY) columns and SIZE rows.
+      Eigen::Map<Eigen::MatrixXd, 0, Eigen::OuterStride<> > data_view() const
+      {
+          return Eigen::Map<Eigen::MatrixXd, 0, Eigen::OuterStride<> >
+              (_data.get(), _parameters.dimX() + _parameters.dimY(), size(),
+               Eigen::OuterStride<>(column_number()));
+      }
+
   protected: // method
 
       //! \brief From a correct input configuration 'x' with size