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Short helpfile for action HISTOGRAM
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The following arguments are compulsory: 

          NORMALIZATION - ( default=ndata ) This controls how the data is normalized 
                          it can be set equal to true, false or ndata. See above for an 
                          explanation 
               GRID_MIN - ( default=auto ) the lower bounds for the grid 
               GRID_MAX - ( default=auto ) the upper bounds for the grid 
                 KERNEL - ( default=GAUSSIAN ) the kernel function you are using. 
                          More details on the kernels available in plumed plumed can be 
                          found in \ref kernelfunctions. 
                 STRIDE - ( default=1 ) the frequency with which to store data for 
                          averaging 
                  CLEAR - ( default=0 ) the frequency with whihc to clear the data 
                          that is being averaged 
            UPDATE_FROM - Only update this action from this time 
           UPDATE_UNTIL - Only update this action until this time 
                    ARG - the quantity that is being averaged 
                   DATA - an alternative to the ARG keyword 
              BANDWIDTH - the bandwidths for kernel density esimtation 
               GRID_BIN - the number of bins for the grid 
           GRID_SPACING - the approximate grid spacing (to be used as an alternative 
                          or together with GRID_BIN) 
             LOGWEIGHTS - the logarithm of the quantity to use as the weights when 
                          calculating averages 


