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Short helpfile for action Q4
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The input trajectory can be in any of the following formats: 

                SPECIES - this keyword is used for colvars such as coordination 
                          number. In that context it specifies that plumed should calculate 
                          one coordination number for each of the atoms specified. Each 
                          of these coordination numbers specifies how many of the other 
                          specified atoms are within a certain cutoff of the central atom. You 
                          can specify the atoms here as another multicolvar action or 
                          using a MultiColvarFilter or ActionVolume action. When you do so 
                          the quantity is calculated for those atoms specified in the 
                          previous multicolvar. This is useful if you would like to calculate 
                          the Steinhardt parameter for those atoms that have a 
                          coordination number more than four for example 
               SPECIESA - this keyword is used for colvars such as the coordination 
                          number. In that context it species that plumed should calculate one 
                          coordination number for each of the atoms specified in SPECIESA. Each of 
                          these coordination numbers specifies how many of the atoms 
                          specifies using SPECIESB is within the specified cutoff. As with the 
                          species keyword the input can also be specified using the label of 
                          another multicolvar 
               SPECIESB - this keyword is used for colvars such as the coordination 
                          number. It must appear with SPECIESA. For a full explanation see 
                          the documentation for that keyword 

The following arguments are compulsory: 

                     NN - ( default=12 ) The n parameter of the switching function 
                     MM - ( default=0 ) The m parameter of the switching function; 0 
                          implies 2*NN 
                    D_0 - ( default=0.0 ) The d_0 parameter of the switching function 
                    R_0 - The r_0 parameter of the switching function 

In addition you may use the following options: 

  NUMERICAL_DERIVATIVES - ( default=off ) calculate the derivatives for these 
                          quantities numerically 
                  NOPBC - ( default=off ) ignore the periodic boundary conditions 
                          when calculating distances 
                 SERIAL - ( default=off ) do the calculation in serial. Do not use 
                          MPI 
                 LOWMEM - ( default=off ) lower the memory requirements 
                TIMINGS - ( default=off ) output information on the timings of the 
                          various parts of the calculation 
                 SWITCH - This keyword is used if you want to employ an alternative 
                          to the continuous switching function defined above. The 
                          following provides information on the \ref switchingfunction that are 
                          available. When this keyword is present you no longer need the NN, MM, 
                          D_0 and R_0 keywords. 
                   MEAN - take the mean of these variables. The final value can be 
                          referenced using <em>label</em>.mean. You can use multiple instances 
                          of this keyword i.e. MEAN1, MEAN2, MEAN3... The corresponding 
                          values are then referenced using <em>label</em>.mean-1, 
                          <em>label</em>.mean-2, <em>label</em>.mean-3... 
              LESS_THAN - calculate the number of variables less than a certain 
                          target value. 
              MORE_THAN - calculate the number of variables more than a certain 
                          target value. 
                  VMEAN - calculate the norm of the mean vector. The final value can 
                          be referenced using <em>label</em>.vmean. You can use multiple 
                          instances of this keyword i.e. VMEAN1, VMEAN2, VMEAN3... The 
                          corresponding values are then referenced using <em>label</em>.vmean-1, 
                          <em>label</em>.vmean-2, <em>label</em>.vmean-3... 
                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. The final value can be 
                          referenced using <em>label</em>.between. You can use multiple 
                          instances of this keyword i.e. BETWEEN1, BETWEEN2, BETWEEN3... The 
                          corresponding values are then referenced using <em>label</em>.between-1, 
                          <em>label</em>.between-2, <em>label</em>.between-3... 
              HISTOGRAM - calculate how many of the values fall in each of the bins 
                          of a histogram. This shortcut allows you to calculates NBIN 
                          quantities like BETWEEN. The final value can be referenced using 
                          <em>label</em>.histogram. You can use multiple instances of this keyword i.e. 
                          HISTOGRAM1, HISTOGRAM2, HISTOGRAM3... The corresponding values are then 
                          referenced using <em>label</em>.histogram-1, 
                          <em>label</em>.histogram-2, <em>label</em>.histogram-3... 
                MOMENTS - calculate the moments of the distribution of collective 
                          variables. 
                    MIN - calculate the minimum value. 
                ALT_MIN - calculate the minimum value. 
                 LOWEST - this flag allows you to recover the lowest of these 
                          variables. The final value can be referenced using 
                          <em>label</em>.lowest 
                HIGHEST - this flag allows you to recover the highest of these 
                          variables. The final value can be referenced using 
                          <em>label</em>.highest 


