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Short helpfile for action DISTANCES
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The input trajectory can be in any of the following formats: 

                  GROUP - Calculate the distance between each distinct pair of atoms 
                          in the group 
                 GROUPA - Calculate the distances between all the atoms in GROUPA and 
                          all the atoms in GROUPB. This must be used in conjunction with 
                          GROUPB. 
                 GROUPB - Calculate the distances between all the atoms in GROUPA and 
                          all the atoms in GROUPB. This must be used in conjunction with 
                          GROUPA. 
                  ATOMS - the pairs of atoms that you would like to calculate the 
                          angles for. You can use multiple instances of this keyword i.e. 
                          ATOMS1, ATOMS2, ATOMS3... 
                 ORIGIN - calculate the distance of all the atoms specified using the 
                          ATOMS keyword from this point. For more information on how to 
                          specify lists of atoms see \ref Group 
               LOCATION - the location at which the CV is assumed to be in space. You 
                          can use multiple instances of this keyword i.e. LOCATION1, 
                          LOCATION2, LOCATION3... 

The following options are available

                  NOPBC - ( default=off ) ignore the periodic boundary conditions 
                          when calculating distances 
             COMPONENTS - ( default=off ) calculate the x, y and z components of the 
                          distance separately and store them as label.x, label.y and label.z 
      SCALED_COMPONENTS - ( default=off ) calculate the a, b and c scaled components 
                          of the distance separately and store them as label.a, label.b 
                          and label.c 
                 LOWMEM - ( default=off ) this flag does nothing and is present only 
                          to ensure back-compatibility 
                HIGHEST - ( default=off ) this flag allows you to recover the highest 
                          of these variables. 
                 LOWEST - ( default=off ) this flag allows you to recover the lowest 
                          of these variables. 
                    SUM - ( default=off ) calculate the sum of all the quantities. 
                   MEAN - ( default=off ) calculate the mean of all the quantities. 
              LESS_THAN - calculate the number of variables that are less than a 
                          certain target value. 
              MORE_THAN - calculate the number of variables that are more than a 
                          certain target value. 
                ALT_MIN - calculate the minimum value. 
                    MIN - calculate the minimum value. 
                    MAX - calculate the maximum value. 
                BETWEEN - calculate the number of values that are within a certain 
                          range. These quantities are calculated using kernel density 
                          estimation as described on \ref histogrambead.. You can use multiple 
                          instances of this keyword i.e. BETWEEN1, BETWEEN2, BETWEEN3... 
              HISTOGRAM - calculate a discretized histogram of the distribution of 
                          values. This shortcut allows you to calculates NBIN quantites like 
                          BETWEEN. 


