AVG

The AVG function takes a vector expression as input and returns the average as a vector with format FLOAT64.

Syntax

Description of the illustration avg_vecse.eps

Purpose

AVG is mainly used to create an overall representation (as in a centroid) for a vector set. In applications like Natural Language Processing (NLP), you can compute the average of several vectors to create a single centroid or overall representation. For example, to represent a sentence, you might average the word embeddings of each word in the sentence. This can be used for tasks like text classification, document similarity, or clustering.

Description of the illustration vector_avg_centroid.png

The result of AVG with a vector expression is the equivalent of consecutively performing vector addition operations on all non-NULL inputs and then dividing by the total number of non-NULL inputs. The returned vector has the same number of dimensions as the input and has the format FLOAT64. When the expression has a flexible number of dimensions, all inputs must have the same number of dimensions within each aggregate group.

The AVG function with vector expressions as input can be used as a single set aggregate or in the GROUP BY clause. Using ROLLUP is also supported. The AVG function accepts vector expressions as input for aggregate operations but cannot currently be applied to analytic operations.

NULL vectors are ignored and are not counted when calculating the average vector. If all inputs within an aggregate group are NULL, the result is NULL for that group. If the result overflows the FLOAT64 maximum value, an error is raised, regardless of the format of the input vector type.

With vector inputs, using DISTINCT, CUBE, and GROUPING SETS is not supported. Also, BINARY and SPARSE vectors cannot be supplied as input.

For the full definition and implementation of the AVG function, see Oracle AI Database SQL Language Reference.

CREATE TABLE avg_t (v VECTOR, k1 NUMBER, k2 VARCHAR2(100));
INSERT INTO avg_t VALUES ('[2, 4, 6]', 2, 'even');
INSERT INTO avg_t VALUES ('[8, 10, 12]', 2, 'even');
INSERT INTO avg_t VALUES ('[1, 3, 5]', 3, 'odd');
INSERT INTO avg_t VALUES ('[7, 9, 11]', 3, 'odd');


SELECT AVG(v) v_avg FROM avg_t;

V_AVG
---------------------------------------------------
[4.5E+000,6.5E+000,8.5E+000]


SELECT AVG(v) v_avg, k1 FROM avg_t GROUP BY k1;

V_AVG                                    K1
---------------------------------------  ----------
[5.0E+000,7.0E+000,9.0E+000]             2
[4.0E+000,6.0E+000,8.0E+000]             3


SELECT AVG(v) v_avg FROM avg_t GROUP BY ROLLUP(k1, k2);

V_AVG
---------------------------------------------------
[5.0E+000,7.0E+000,9.0E+000]
[5.0E+000,7.0E+000,9.0E+000]
[4.0E+000,6.0E+000,8.0E+000]
[4.0E+000,6.0E+000,8.0E+000]
[4.5E+000,6.5E+000,8.5E+000]