110 lines
2.0 KiB
Markdown
110 lines
2.0 KiB
Markdown
# Distance
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Selected algorithms require the use of a function for calculating the distance.
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### Euclidean
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Class for calculating Euclidean distance.
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To calculate Euclidean distance:
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```
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$a = [4, 6];
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$b = [2, 5];
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$euclidean = new Euclidean();
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$euclidean->distance($a, $b);
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// return 2.2360679774998
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```
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### Manhattan
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Class for calculating Manhattan distance.
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To calculate Manhattan distance:
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```
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$a = [4, 6];
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$b = [2, 5];
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$manhattan = new Manhattan();
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$manhattan->distance($a, $b);
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// return 3
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```
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### Chebyshev
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Class for calculating Chebyshev distance.
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To calculate Chebyshev distance:
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```
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$a = [4, 6];
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$b = [2, 5];
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$chebyshev = new Chebyshev();
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$chebyshev->distance($a, $b);
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// return 2
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```
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### Minkowski
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Class for calculating Minkowski distance.
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To calculate Minkowski distance:
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```
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$a = [4, 6];
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$b = [2, 5];
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$minkowski = new Minkowski();
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$minkowski->distance($a, $b);
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// return 2.080
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```
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You can provide the `lambda` parameter:
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```
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$a = [6, 10, 3];
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$b = [2, 5, 5];
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$minkowski = new Minkowski($lambda = 5);
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$minkowski->distance($a, $b);
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// return 5.300
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```
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### Custom distance
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To apply your own function of distance use the `Distance` interface. Example:
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```
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class CustomDistance implements Distance
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{
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/**
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* @param array $a
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* @param array $b
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*
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* @return float
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*/
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public function distance(array $a, array $b) : float
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{
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$distance = [];
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$count = count($a);
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for ($i = 0; $i < $count; ++$i) {
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$distance[] = $a[$i] * $b[$i];
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}
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return min($distance);
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}
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}
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```
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