Similarity

java.lang.Object
- org.ojalgo.data.proximity.Similarity

```
public abstract class Similarity
extends java.lang.Object
```
Similarity / distance utilities commonly used in ML and information retrieval. Provides cosine similarity ([-1,1]) and cosine distance (1 - cosine similarity). Overloads are provided for both raw double[] and Access1D (treated as linearised 1D vectors using their element order).

Constructor Summary

Constructors
Constructor Description

Similarity()

Method Summary

All Methods Static Methods Concrete Methods
Modifier and Type	Method	Description
`static double`	`cosine(double[] a, double[] b)`	Cosine similarity between two equal-length vectors.
`static double`	`cosine(Access1D<?> a, Access1D<?> b)`	Cosine similarity between 2 matrices treated as flattened vectors.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - Similarity
```
public Similarity()
```
- Method Detail
  - cosine
```
public static double cosine(Access1D<?> a,
                            Access1D<?> b)
```
    Cosine similarity between 2 matrices treated as flattened vectors.
    
    Parameters:
    
    a - matrix a
    
    b - matrix b
    
    Returns:
    
    cosine similarity in [-1, 1]
    
    Throws:
    
    java.lang.NullPointerException - if a or b is null
    
    java.lang.IllegalArgumentException - if element counts differ or either has zero norm
  - cosine
```
public static double cosine(double[] a,
                            double[] b)
```
    Cosine similarity between two equal-length vectors.
    
    Parameters:
    
    a - vector a
    
    b - vector b
    
    Returns:
    
    cosine similarity in [-1, 1]
    
    Throws:
    
    java.lang.NullPointerException - if a or b is null
    
    java.lang.IllegalArgumentException - if lengths differ or either vector has zero norm