The Nf parameter denotes a range filter request.

A range filter request requires an Nf parameter. However, because a range filter is actually a modifier for a basic navigation request, it must be accompanied by a standard N navigation request (even if that basic navigation request is empty).

Only records returned by the basic navigation request (N) are considered when evaluating the range filter. (Range filters and navigation dimension values together form a Boolean AND request.)

The Nf parameter has the following syntax:

Nf=filter-key|function[+geo-ref]+value[+value]

The single range filter parameter specifies three separate components of a complete range filter:

filter-key is the name of a numeric property, geocode property, or numeric dimension. Only a single property key can be specified per range filter.

function is one of the following:

value is one or more numeric fields defining the actual range. The LT, LTEQ, GT, and GTEQ functions require only a single value. The BTWN function requires two value settings, with the smaller value listed first and the larger value listed next, separated by a plus sign (+) delimiter.

geo-ref is a geocode reference point that must be specified if one of the geocode functions has been specified (GCLT, GCGT, GCBTWN). This is the only case where a geocode reference point may be specified. When a geocode filter is specified, the records are filtered by the distance from the filter key (a geocode property) to geo-ref (the geocode reference point).