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Lextek Language Identifier
P_ORDERED_NEAR
Name
P_ORDERED_NEAR
Synopsis
Returns records where the listed terms or subqueries are within a specified number of words and are in the same order as listed.
Arguments
Maximum distance between the words
List of terms and subqueriesRanking Scheme
Ranks using the p-norm method. Conceptually you can consider each term a unique direction in n-space (where n is the number of terms). Each term's weight represents the distance in that direction. The p-value (p in the above formula) represents how much the final calculation is like the maximum weight or like the total distance of all vectors in n-space. For p = 2 the p-norm is identical to a vector space model. As p approaches infinity the returned weight becomes equal to the largest weight among the terms.
Picking an appropriate p-value can be tricky and often is the result of experimentation. A simplified way of thinking about the calculation is that it varies between a kind of average weight to the maximum weight. Generally a p-value of 2.5 or 3 is effective.
The p-norm weighting method is one of the most efficient methods available, especially if you've been careful in choosing how you weight your terms.
Note that the p-norm calculation for P_ORDERED_NEAR is the same as for P_AND.
Comments
P_ORDERED_NEAR combines the features of NEAR and PHRASE. It is like a PHRASE in that each term or subquery must occur in the order they are listed. It differs in that they need not be adjacent. They must, however, be within the specified number of words.
Note that while we say, "within n words," what counts as a word is specified by the indexing process. Each call to prIndexWord increments the word count.
Example
P_ORDERED_NEAR( 2.5, 3 'blue', 'green' );
See Also
near, r_near, p_near, v_near, ordered_near, r_ordered_near, p_ordered_near, v_ordered_near
