                  ┌                                        ┐ 
   [-60.0, -40.0) ┤▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇ 1                     
   [-40.0, -20.0) ┤▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇ 2   
   [-20.0,   0.0) ┤▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇ 2   
   [  0.0,  20.0) ┤▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇ 1                     
   [ 20.0,  40.0) ┤▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇ 2   
   [ 40.0,  60.0) ┤▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇ 2   
                  └                                        ┘ 
                                  Frequency
