docs: @Override
      public double getY(double x)
      {
          double slope = getSlope();
          double a = getYIntercept(slope);
          if (!Double.isInfinite(slope))
          {
              return slope*x + a;
          }
          else
          {
              if (x == a)
              {
                  return Double.POSITIVE_INFINITY;
              }
              else
              {
                  return Double.NaN;
              }
          }
      }