Make sensitivity accept floats for better precision

src/AnomalyDetectionResult.php

@@ -54,8 +54,8 @@
     /** @var float The mean value */
     private float $mean;
 
-    /** @var int The sensitivity */
-    private int $sensitivity;
+    /** @var float|int The sensitivity */
+    private float|int $sensitivity;
 
     /** @var float The low bound */
     private float $low;
@@ -78,29 +78,29 @@
      * @param float $std_dev The standard deviation
      * @param float $mean The mean value
      * @param float $latest The latest value
-     * @param int $sensitivity The sensitivity (see `SlidingWindowCounter::detectAnomaly()`)
+     * @param float|int $sensitivity The sensitivity (see `SlidingWindowCounter::detectAnomaly()`)
      */
-    public function __construct(float $std_dev, float $mean, float $latest, int $sensitivity)
+    public function __construct(float $std_dev, float $mean, float $latest, float|int $sensitivity)
     {
         $this->std_dev = $std_dev;
         $this->mean = $mean;
         $this->latest = $latest;
         $this->sensitivity = $sensitivity;
 
         $this->high = ceil($this->mean + ($sensitivity * $this->std_dev));
         $this->low = floor($this->mean - ($sensitivity * $this->std_dev));
 
         if ($this->latest >= $this->low && $this->latest <= $this->high) {
             return;
         }
 
         if ($this->std_dev > 0.0) {
             $this->hops = abs($this->mean - $this->latest) / $this->std_dev;
         }
 
         if ($this->latest < $this->low) {
             $this->direction = self::DIRECTION_DOWN;
         } elseif ($this->latest > $this->high) {
             $this->direction = self::DIRECTION_UP;
         }
     }
@@ -118,7 +118,7 @@
      *
      * @param int $precision the number of decimal digits to round to
      */
     public function toArray(int $precision = 2): array
     {
         return array_map(
             fn ($val) => is_float($val) ? round($val, $precision) : $val,
@@ -145,7 +145,7 @@
     /**
      * The sensitivity.
      */
-    public function getSensitivity(): int
+    public function getSensitivity(): float|int
     {
         return $this->sensitivity;
     }

src/SlidingWindowCounter.php

@@ -241,10 +241,10 @@ public function getLatestValue(string $bucket_key): float
      * Tests the standard deviation against the acceptable range and returns the alert message.
      *
      * @param string $bucket_key The bucket key
-     * @param int $sensitivity The sensitivity: 3 = low (99.7%), 2 = standard (95%) 1 = high (68% deviation triggers alert)
+     * @param float|int $sensitivity The sensitivity: 3 = low (99.7%), 2 = standard (95%) 1 = high (68% deviation triggers alert)
      * @param null|int $start_time The optional start time; leaving out the start time will omit the leading null values
      */
-    public function detectAnomaly(string $bucket_key, int $sensitivity = 2, ?int $start_time = null): AnomalyDetectionResult
+    public function detectAnomaly(string $bucket_key, float|int $sensitivity = 2, ?int $start_time = null): AnomalyDetectionResult
     {
         $variance = $this->getHistoricVariance($bucket_key, $start_time);
 

tests/AnomalyDetectionResultTest.php

@@ -57,11 +57,11 @@ public function testHappyPath(): void
      */
     public function testAllGetters(): void
     {
-        $result = new AnomalyDetectionResult(1.0, 10.0, 11.0, 1);
+        $result = new AnomalyDetectionResult(1.0, 10.0, 11.0, 0.9);
 
         $this->assertSame(1.0, $result->getStandardDeviation());
         $this->assertSame(10.0, $result->getMean());
-        $this->assertSame(1, $result->getSensitivity());
+        $this->assertSame(0.9, $result->getSensitivity());
         $this->assertSame(9.0, $result->getLow());
         $this->assertSame(11.0, $result->getHigh());
         $this->assertSame(11.0, $result->getLatest());