[Summary view]

Differences Between: [Versions 400 and 401]

   1  <?php
   2  
   3  namespace PhpOffice\PhpSpreadsheet\Calculation\Statistical\Distributions;
   4  
   5  use PhpOffice\PhpSpreadsheet\Calculation\ArrayEnabled;
   6  use PhpOffice\PhpSpreadsheet\Calculation\Exception;
   7  use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
   8  
   9  class Exponential
  10  {
  11      use ArrayEnabled;
  12  
  13      /**
  14       * EXPONDIST.
  15       *
  16       *    Returns the exponential distribution. Use EXPONDIST to model the time between events,
  17       *        such as how long an automated bank teller takes to deliver cash. For example, you can
  18       *        use EXPONDIST to determine the probability that the process takes at most 1 minute.
  19       *
  20       * @param mixed $value Float value for which we want the probability
  21       *                      Or can be an array of values
  22       * @param mixed $lambda The parameter value as a float
  23       *                      Or can be an array of values
  24       * @param mixed $cumulative Boolean value indicating if we want the cdf (true) or the pdf (false)
  25       *                      Or can be an array of values
  26       *
  27       * @return array|float|string
  28       *         If an array of numbers is passed as an argument, then the returned result will also be an array
  29       *            with the same dimensions
  30       */
  31      public static function distribution($value, $lambda, $cumulative)
  32      {
  33          if (is_array($value) || is_array($lambda) || is_array($cumulative)) {
  34              return self::evaluateArrayArguments([self::class, __FUNCTION__], $value, $lambda, $cumulative);
  35          }
  36  
  37          try {
  38              $value = DistributionValidations::validateFloat($value);
  39              $lambda = DistributionValidations::validateFloat($lambda);
  40              $cumulative = DistributionValidations::validateBool($cumulative);
  41          } catch (Exception $e) {
  42              return $e->getMessage();
  43          }
  44  
  45          if (($value < 0) || ($lambda < 0)) {
  46              return ExcelError::NAN();
  47          }
  48  
  49          if ($cumulative === true) {
  50              return 1 - exp(0 - $value * $lambda);
  51          }
  52  
  53          return $lambda * exp(0 - $value * $lambda);
  54      }
  55  }