function Vector::correlation in Recommender API 6.2

Same name and namespace in other branches

1. 7.6 classes/Matrix.php \Vector::correlation()

Compute correlation with $vector. No caching option. Works for RealVector. SparseVector needs additional handling.

Parameters

$vector it has to be the same type (either SparseVector or RealVector) as $this:

Return value

correlation value

1 method overrides Vector::correlation()

SparseVector::correlation in ./Matrix.php

Compute correlation with $vector. No caching option. Works for RealVector. SparseVector needs additional handling.

File

./Matrix.php, line 276

Class

Vector

This is the Vector superclass. @author danithaca

Code

function correlation(&$vector) {
  $covariance = $this
    ->covariance($vector);
  if (is_nan($covariance)) {
    return NAN;
  }

  // might use cached std.
  $std_a = $this
    ->std(TRUE);
  $std_b = $vector
    ->std(TRUE);
  return $std_a == 0 || $std_b == 0 ? NAN : $covariance / ($std_a * $std_b);
}