ndhist

Lightweight histogram class for filling and saving to HDF5.

Histograms can be arbitrary dimensions (up to 32 can be saved by HDF5). The result is saved as a HDF5 DataSet, with attributes indicating the binning. Attributes are saved as an array, with the Nth entry in the array corresponding to the Nth axis. The following attributes are saved:

• names: axis names, each axis must have a unique name
• n_bins: number of bins in this axis (not including overflow)
• min: bottom range of the axis
• max: upper range of the axis
• units: (optional) string indicating units

Constructor Flags

Several flags can be passed to the Histogram constructor.

• hist::wt2: Fill a second histogram with weights of weight^2. The second histogram will be saved as "Wt2". This is useful to calculate statistical error in weighted samples, but will double the amount of space required in memory / on disk.

• hist::eat_nan: Without this flag, passing fill(...) NaN results in a std::range_error. With it, Histogram will record the number of times NaN is passed, and save an additional attribute nan. There is only one NaN counter for all axes.