Obtains the relative frequency of occurrence of items in a data object.
Items are collected into regularly spaced output bins whose size
is specified by the user. The first bin starts at the minimum of
the data in the input object so its centre is at
and so on.
The normalisation option, when used, makes the sum (not a numerical integral) of the frequency bins equal to unity.
Data quality is taken into account if present in the input data object: items in the input whose quality is not perfect are ignored.