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Diffstat (limited to 'library/Icinga/Chart/Unit/LogarithmicUnit.php')
| -rw-r--r-- | library/Icinga/Chart/Unit/LogarithmicUnit.php | 263 |
1 files changed, 263 insertions, 0 deletions
diff --git a/library/Icinga/Chart/Unit/LogarithmicUnit.php b/library/Icinga/Chart/Unit/LogarithmicUnit.php new file mode 100644 index 0000000..90cad57 --- /dev/null +++ b/library/Icinga/Chart/Unit/LogarithmicUnit.php @@ -0,0 +1,263 @@ +<?php +/* Icinga Web 2 | (c) 2013 Icinga Development Team | GPLv2+ */ + +namespace Icinga\Chart\Unit; + +/** + * Logarithmic tick distribution over the axis + * + * This class does not use the actual logarithm, but a slightly altered version called the + * Log-Modulo transformation. This is necessary, since a regular logarithmic scale is not able to display negative + * values and zero-points. See <a href="http://blogs.sas.com/content/iml/2014/07/14/log-transformation-of-pos-neg> + * this article </a> for a more detailed description. + */ +class LogarithmicUnit implements AxisUnit +{ + /** + * @var int + */ + protected $base; + + /** + * @var + */ + protected $currentTick; + + /** + * @var + */ + protected $minExp; + + /** + * @var + */ + protected $maxExp; + + /** + * True when the minimum value is static and isn't affected by the data set + * + * @var bool + */ + protected $staticMin = false; + + /** + * True when the maximum value is static and isn't affected by the data set + * + * @var bool + */ + protected $staticMax = false; + + /** + * Create and initialize this AxisUnit + * + * @param int $nrOfTicks The number of ticks to use + */ + public function __construct($base = 10) + { + $this->base = $base; + $this->minExp = PHP_INT_MAX; + $this->maxExp = ~PHP_INT_MAX; + } + + /** + * Add a dataset and calculate the minimum and maximum value for this AxisUnit + * + * @param array $dataset The dataset to add + * @param int $idx The idx (0 for x, 1 for y) + * + * @return $this Fluent interface + */ + public function addValues(array $dataset, $idx = 0) + { + $datapoints = array(); + + foreach ($dataset['data'] as $points) { + $datapoints[] = $points[$idx]; + } + if (empty($datapoints)) { + return $this; + } + sort($datapoints); + if (!$this->staticMax) { + $this->maxExp = max($this->maxExp, $this->logCeil($datapoints[count($datapoints) - 1])); + } + if (!$this->staticMin) { + $this->minExp = min($this->minExp, $this->logFloor($datapoints[0])); + } + $this->currentTick = 0; + + return $this; + } + + /** + * Transform the absolute value to an axis relative value + * + * @param int $value The absolute coordinate from the data set + * @return float|int The axis relative coordinate (between 0 and 100) + */ + public function transform($value) + { + if ($value < $this->pow($this->minExp)) { + return 0; + } elseif ($value > $this->pow($this->maxExp)) { + return 100; + } else { + return 100 * ($this->log($value) - $this->minExp) / $this->getTicks(); + } + } + + /** + * Return the position of the current tick + * + * @return int + */ + public function current() + { + return $this->currentTick * (100 / $this->getTicks()); + } + + /** + * Calculate the next tick and tick value + */ + public function next() + { + ++ $this->currentTick; + } + + /** + * Return the label for the current tick + * + * @return string The label for the current tick + */ + public function key() + { + $currentBase = $this->currentTick + $this->minExp; + if (abs($currentBase) > 4) { + return $this->base . 'E' . $currentBase; + } + return (string) intval($this->pow($currentBase)); + } + + /** + * True when we're at a valid tick (iterator interface) + * + * @return bool + */ + public function valid() + { + return $this->currentTick >= 0 && $this->currentTick < $this->getTicks(); + } + + /** + * Reset the current tick and label value + */ + public function rewind() + { + $this->currentTick = 0; + } + + /** + * Perform a log-modulo transformation + * + * @param $value The value to transform + * + * @return double The transformed value + */ + protected function log($value) + { + $sign = $value > 0 ? 1 : -1; + return $sign * log1p($sign * $value) / log($this->base); + } + + /** + * Calculate the biggest exponent necessary to display the given data point + * + * @param $value + * + * @return float + */ + protected function logCeil($value) + { + return ceil($this->log($value)) + 1; + } + + /** + * Calculate the smallest exponent necessary to display the given data point + * + * @param $value + * + * @return float + */ + protected function logFloor($value) + { + return floor($this->log($value)); + } + + /** + * Inverse function to the log-modulo transformation + * + * @param $value + * + * @return double + */ + protected function pow($value) + { + if ($value == 0) { + return 0; + } + $sign = $value > 0 ? 1 : -1; + return $sign * (pow($this->base, $sign * $value)); + } + + /** + * Set the axis minimum value to a fixed value + * + * @param int $min The new minimum value + */ + public function setMin($min) + { + $this->minExp = $this->logFloor($min); + $this->staticMin = true; + } + + /** + * Set the axis maximum value to a fixed value + * + * @param int $max The new maximum value + */ + public function setMax($max) + { + $this->maxExp = $this->logCeil($max); + $this->staticMax = true; + } + + /** + * Return the current minimum value of the axis + * + * @return int The minimum set for this axis + */ + public function getMin() + { + return $this->pow($this->minExp); + } + + /** + * Return the current maximum value of the axis + * + * @return int The maximum set for this axis + */ + public function getMax() + { + return $this->pow($this->maxExp); + } + + /** + * Get the amount of ticks necessary to display this AxisUnit + * + * @return int + */ + public function getTicks() + { + return $this->maxExp - $this->minExp; + } +} |