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Differences Between: [Versions 310 and 401] [Versions 311 and 401] [Versions 39 and 401]

   1  <?php
   2  
   3  namespace PhpOffice\PhpSpreadsheet\Shared\Trend;
   4  
   5  class PowerBestFit extends BestFit
   6  {
   7      /**
   8       * Algorithm type to use for best-fit
   9       * (Name of this Trend class).
  10       *
  11       * @var string
  12       */
  13      protected $bestFitType = 'power';
  14  
  15      /**
  16       * Return the Y-Value for a specified value of X.
  17       *
  18       * @param float $xValue X-Value
  19       *
  20       * @return float Y-Value
  21       */
  22      public function getValueOfYForX($xValue)
  23      {
  24          return $this->getIntersect() * ($xValue - $this->xOffset) ** $this->getSlope();
  25      }
  26  
  27      /**
  28       * Return the X-Value for a specified value of Y.
  29       *
  30       * @param float $yValue Y-Value
  31       *
  32       * @return float X-Value
  33       */
  34      public function getValueOfXForY($yValue)
  35      {
  36          return (($yValue + $this->yOffset) / $this->getIntersect()) ** (1 / $this->getSlope());
  37      }
  38  
  39      /**
  40       * Return the Equation of the best-fit line.
  41       *
  42       * @param int $dp Number of places of decimal precision to display
  43       *
  44       * @return string
  45       */
  46      public function getEquation($dp = 0)
  47      {
  48          $slope = $this->getSlope($dp);
  49          $intersect = $this->getIntersect($dp);
  50  
  51          return 'Y = ' . $intersect . ' * X^' . $slope;
  52      }
  53  
  54      /**
  55       * Return the Value of X where it intersects Y = 0.
  56       *
  57       * @param int $dp Number of places of decimal precision to display
  58       *
  59       * @return float
  60       */
  61      public function getIntersect($dp = 0)
  62      {
  63          if ($dp != 0) {
  64              return round(exp($this->intersect), $dp);
  65          }
  66  
  67          return exp($this->intersect);
  68      }
  69  
  70      /**
  71       * Execute the regression and calculate the goodness of fit for a set of X and Y data values.
  72       *
  73       * @param float[] $yValues The set of Y-values for this regression
  74       * @param float[] $xValues The set of X-values for this regression
  75       */
  76      private function powerRegression(array $yValues, array $xValues, bool $const): void
  77      {
  78          $adjustedYValues = array_map(
  79              function ($value) {
  80                  return ($value < 0.0) ? 0 - log(abs($value)) : log($value);
  81              },
  82              $yValues
  83          );
  84          $adjustedXValues = array_map(
  85              function ($value) {
  86                  return ($value < 0.0) ? 0 - log(abs($value)) : log($value);
  87              },
  88              $xValues
  89          );
  90  
  91          $this->leastSquareFit($adjustedYValues, $adjustedXValues, $const);
  92      }
  93  
  94      /**
  95       * Define the regression and calculate the goodness of fit for a set of X and Y data values.
  96       *
  97       * @param float[] $yValues The set of Y-values for this regression
  98       * @param float[] $xValues The set of X-values for this regression
  99       * @param bool $const
 100       */
 101      public function __construct($yValues, $xValues = [], $const = true)
 102      {
 103          parent::__construct($yValues, $xValues);
 104  
 105          if (!$this->error) {
 106              $this->powerRegression($yValues, $xValues, (bool) $const);
 107          }
 108      }
 109  }