acos

Generic Description

Computes arccosine and returns an angle in radians. It is documented separately because numeric transforms change ranking, thresholds, and buckets in ways planner tools must not guess.

Simple example:

RETURN acos(0.5) AS value

Consumer-Level Explanation

Use it to convert cosine similarity-like values back into angular distance when that interpretation is useful. Prefer this function when the transformation is a deliberate part of the model or report, and name the derived value in a WITH stage when it will be reused.

More Detailed Explanation

acos is scalar math, so it is evaluated per row after graph patterns, procedure output, or map projections have produced values. Keep it close to the query when thresholds, ranking, and derived fields need to be auditable and reproducible.

Advanced Example

This example applies acos to a named score component after matching graph data, making the derived metric reviewable before ordering.

MATCH (d:Document)
WITH d, cosine_similarity(vector(properties(d).embedding), vector([0.22, 0.18, 0.44])) AS similarity
RETURN d.title AS document,
       acos(similarity) AS angular_distance
ORDER BY angular_distance ASC

Real Use Cases

• distance-from-target scoring
• numeric bucketing and normalization before ORDER BY or aggregation
• making scoring formulas visible to query review and assistant tooling

Real Limitations And Tradeoffs

• invalid numeric inputs produce null-like results rather than a repaired value
• math functions do not fix poor feature scaling; choose transformations intentionally
• nondeterministic functions such as random sampling are not appropriate for persisted decisions