Indexed sequential access methods allow finding the keys (having associations) closest to a given value. This facilitates the interpolation of associations between those in the table.
Table should be a relational table with one numeric primary key field which supports the
isam-nextoperations. column should be a symbol or exact positive integer designating a numerically valued column of table.
interpolate-from-tablecalculates and returns a value proportionally intermediate between its values in the next and previous key records contained in table. For keys larger than all the stored keys the value associated with the largest stored key is used. For keys smaller than all the stored keys the value associated with the smallest stored key is used.