Percentile() - allow different calculation types (as in TERR) for calculated columns

TERR allows 3 discrete and 6 continuos calculation variants for quantile() which ends in different results. It can be controlled by optional 3rd parameter. Default value is 7. However expression language used for calculated columns only supports that type 7 calculation which is a continuos variant.

Would be mandatory to add at least one discrete option - as ORACLE or MySQL do mit PERCENTILE_DISC(). But best would be to work in same manner in TERR with an optional parameter controlling the variant to use.

Full (9) options are required to match Spotfire calculations which those done in other programs like SPSS or Minitab.

(see my case 02102568 for reference)