[Summary view]

Differences Between: [Versions 400 and 401] [Versions 400 and 402] [Versions 400 and 403]

   1  <?php
   2  
   3  namespace PhpOffice\PhpSpreadsheet\Calculation\Statistical\Distributions;
   4  
   5  use PhpOffice\PhpSpreadsheet\Calculation\Functions;
   6  use PhpOffice\PhpSpreadsheet\Calculation\Statistical\Averages;
   7  use PhpOffice\PhpSpreadsheet\Calculation\Statistical\StandardDeviations;
   8  
   9  class StandardNormal
  10  {
  11      /**
  12       * NORMSDIST.
  13       *
  14       * Returns the standard normal cumulative distribution function. The distribution has
  15       * a mean of 0 (zero) and a standard deviation of one. Use this function in place of a
  16       * table of standard normal curve areas.
  17       *
  18       * @param mixed $value Float value for which we want the probability
  19       *
  20       * @return float|string The result, or a string containing an error
  21       */
  22      public static function cumulative($value)
  23      {
  24          return Normal::distribution($value, 0, 1, true);
  25      }
  26  
  27      /**
  28       * NORM.S.DIST.
  29       *
  30       * Returns the standard normal cumulative distribution function. The distribution has
  31       * a mean of 0 (zero) and a standard deviation of one. Use this function in place of a
  32       * table of standard normal curve areas.
  33       *
  34       * @param mixed $value Float value for which we want the probability
  35       * @param mixed $cumulative Boolean value indicating if we want the cdf (true) or the pdf (false)
  36       *
  37       * @return float|string The result, or a string containing an error
  38       */
  39      public static function distribution($value, $cumulative)
  40      {
  41          return Normal::distribution($value, 0, 1, $cumulative);
  42      }
  43  
  44      /**
  45       * NORMSINV.
  46       *
  47       * Returns the inverse of the standard normal cumulative distribution
  48       *
  49       * @param mixed $value Float probability for which we want the value
  50       *
  51       * @return float|string The result, or a string containing an error
  52       */
  53      public static function inverse($value)
  54      {
  55          return Normal::inverse($value, 0, 1);
  56      }
  57  
  58      /**
  59       * GAUSS.
  60       *
  61       * Calculates the probability that a member of a standard normal population will fall between
  62       *     the mean and z standard deviations from the mean.
  63       *
  64       * @param mixed $value
  65       *
  66       * @return float|string The result, or a string containing an error
  67       */
  68      public static function gauss($value)
  69      {
  70          $value = Functions::flattenSingleValue($value);
  71          if (!is_numeric($value)) {
  72              return Functions::VALUE();
  73          }
  74  
  75          return self::distribution($value, true) - 0.5;
  76      }
  77  
  78      /**
  79       * ZTEST.
  80       *
  81       * Returns the one-tailed P-value of a z-test.
  82       *
  83       * For a given hypothesized population mean, x, Z.TEST returns the probability that the sample mean would be
  84       *     greater than the average of observations in the data set (array) — that is, the observed sample mean.
  85       *
  86       * @param mixed $dataSet The dataset should be an array of float values for the observations
  87       * @param mixed $m0 Alpha Parameter
  88       * @param mixed $sigma A null or float value for the Beta (Standard Deviation) Parameter;
  89       *                       if null, we use the standard deviation of the dataset
  90       *
  91       * @return float|string (string if result is an error)
  92       */
  93      public static function zTest($dataSet, $m0, $sigma = null)
  94      {
  95          $dataSet = Functions::flattenArrayIndexed($dataSet);
  96          $m0 = Functions::flattenSingleValue($m0);
  97          $sigma = Functions::flattenSingleValue($sigma);
  98  
  99          if (!is_numeric($m0) || ($sigma !== null && !is_numeric($sigma))) {
 100              return Functions::VALUE();
 101          }
 102  
 103          if ($sigma === null) {
 104              $sigma = StandardDeviations::STDEV($dataSet);
 105          }
 106          $n = count($dataSet);
 107  
 108          return 1 - self::cumulative((Averages::average($dataSet) - $m0) / ($sigma / sqrt($n)));
 109      }
 110  }