Test plot                                               
     10 +-------------------------------------------------------------------------------+ 30        
        |         +         +         +         +         +         +         +      ** |           
        |                                                                data 0 ***A*** |           
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      9 |-+                                                                  ***        |           
        |                                                                  **         +#| 25        
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      8 |-+                                                        *A*           ##     |           
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        |                                                   **             ##         +-| 20        
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      6 |-+                                    *A*               ##                   +-| 15        
  y     |                                    **               ###                       |    y2     
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      5 |-+                         **              ###                                 |           
        |                         **              ##                                  +-| 10        
        |                       **             #B#                                      |           
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      4 |-+                *A*          ###                                             |           
        |                **          ###                                                |           
        |             ***        ####                                                 +-| 5         
        |           **        ###                                                       |           
      3 |-+      ***     ###B#                                                          |           
        |      ** #######                                                               |           
        |   ######                                                                      |           
        |###      +         +         +         +         +         +         +         |           
      2 +-------------------------------------------------------------------------------+ 0         
        1        1.5        2        2.5        3        3.5        4        4.5        5           
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