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<?php |
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namespace Samsara\Fermat\Provider; |
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use Ds\Vector; |
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use Samsara\Exceptions\UsageError\IntegrityConstraint; |
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use Samsara\Exceptions\SystemError\LogicalError\IncompatibleObjectState; |
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use Samsara\Exceptions\UsageError\OptionalExit; |
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use Samsara\Fermat\Numbers; |
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use Samsara\Fermat\Types\Base\Interfaces\Numbers\NumberInterface; |
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use Samsara\Fermat\Types\Base\Interfaces\Numbers\DecimalInterface; |
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use Samsara\Fermat\Types\Base\Interfaces\Numbers\FractionInterface; |
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use Samsara\Fermat\Values\ImmutableDecimal; |
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use Samsara\Fermat\Values\ImmutableFraction; |
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class StatsProvider |
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{ |
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/** |
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* @var Vector |
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*/ |
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protected static $inverseErrorCoefs; |
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/** |
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* @param $x |
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* |
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* @return NumberInterface |
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* @throws IntegrityConstraint |
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* @throws OptionalExit|\ReflectionException |
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*/ |
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public static function normalCDF($x): ImmutableDecimal |
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{ |
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$x = Numbers::makeOrDont(Numbers::IMMUTABLE, $x); |
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$precision = $x->getPrecision(); |
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$internalPrecision = $precision+2; |
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$pi = Numbers::makePi($internalPrecision); |
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$e = Numbers::makeE($internalPrecision); |
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$one = Numbers::makeOne($internalPrecision); |
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$eExponent = Numbers::make(Numbers::IMMUTABLE, $x->getValue()); |
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$eExponent = $eExponent->pow(2)->divide(2)->multiply(-1); |
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$answer = Numbers::make(Numbers::IMMUTABLE, 0.5); |
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$answer = $answer->add( |
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$one->divide($pi->multiply(2)->sqrt()) |
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->multiply($e->pow($eExponent)) |
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->multiply(SeriesProvider::maclaurinSeries( |
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$x, |
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function ($n) { |
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return Numbers::makeOne(); |
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}, |
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function ($n) { |
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return SequenceProvider::nthOddNumber($n); |
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}, |
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function ($n) { |
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return SequenceProvider::nthOddNumber($n)->doubleFactorial(); |
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}, |
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0, |
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$internalPrecision |
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)) |
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); |
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return $answer->truncateToPrecision($precision); |
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} |
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/** |
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* @param $x |
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* |
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* @return DecimalInterface|NumberInterface |
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* @throws IntegrityConstraint |
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* @throws OptionalExit |
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*/ |
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public static function complementNormalCDF($x): ImmutableDecimal |
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{ |
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$p = self::normalCDF($x); |
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$one = Numbers::makeOne(); |
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return $one->subtract($p); |
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} |
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/** |
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* @param $x |
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* |
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* @return DecimalInterface|FractionInterface|NumberInterface|ImmutableDecimal |
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* @throws IntegrityConstraint |
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* @throws OptionalExit |
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*/ |
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public static function gaussErrorFunction($x): ImmutableDecimal |
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{ |
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$x = Numbers::makeOrDont(Numbers::IMMUTABLE, $x); |
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$precision = $x->getPrecision(); |
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$internalPrecision = $precision + 2; |
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$answer = Numbers::makeOne($internalPrecision); |
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$pi = Numbers::makePi($internalPrecision); |
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$answer = $answer->multiply(2)->divide($pi->sqrt()); |
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$answer = $answer->multiply( |
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SeriesProvider::maclaurinSeries( |
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$x, |
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function ($n) { |
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$negOne = Numbers::make(Numbers::IMMUTABLE, -1); |
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return $negOne->pow($n); |
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}, |
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function ($n) { |
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return SequenceProvider::nthOddNumber($n); |
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}, |
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function ($n) { |
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$n = Numbers::makeOrDont(Numbers::IMMUTABLE, $n); |
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return $n->factorial()->multiply(SequenceProvider::nthOddNumber($n->asInt())); |
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}, |
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0, |
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$internalPrecision |
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) |
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); |
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return $answer->truncateToPrecision($precision); |
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} |
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/** |
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* @param $p |
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* @param int $precision |
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* |
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* @return DecimalInterface|NumberInterface|ImmutableDecimal |
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* @throws IntegrityConstraint |
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* @throws OptionalExit |
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*/ |
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public static function inverseNormalCDF($p, int $precision = 10): ImmutableDecimal |
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{ |
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$p = Numbers::makeOrDont(Numbers::IMMUTABLE, $p); |
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$precision = $precision ?? $p->getPrecision(); |
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$internalPrecision = $precision + 2; |
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$two = Numbers::make(Numbers::IMMUTABLE, 2, $internalPrecision); |
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$invErfArg = $two->multiply($p)->subtract(1); |
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return StatsProvider::inverseGaussErrorFunction($invErfArg, $internalPrecision)->multiply($two->sqrt($internalPrecision))->roundToPrecision($precision); |
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} |
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/** |
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* @param $n |
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* @param $k |
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* |
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* @return DecimalInterface|NumberInterface|ImmutableDecimal |
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* @throws IntegrityConstraint |
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* @throws IncompatibleObjectState |
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*/ |
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public static function binomialCoefficient($n, $k): ImmutableDecimal |
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{ |
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$n = Numbers::makeOrDont(Numbers::IMMUTABLE, $n); |
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$k = Numbers::makeOrDont(Numbers::IMMUTABLE, $k); |
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if ($k->isLessThan(0) || $n->isLessThan($k)) { |
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throw new IntegrityConstraint( |
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'$k must be larger or equal to 0 and less than or equal to $n', |
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'Provide valid $n and $k values such that 0 <= $k <= $n', |
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'For $n choose $k, the values of $n and $k must satisfy the inequality 0 <= $k <= $n' |
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); |
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} |
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if (!$n->isInt() || !$k->isInt()) { |
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throw new IntegrityConstraint( |
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'$k and $n must be whole numbers', |
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'Provide whole numbers for $n and $k', |
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'For $n choose $k, the values $n and $k must be whole numbers' |
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); |
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} |
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return $n->factorial()->divide($k->factorial()->multiply($n->subtract($k)->factorial())); |
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} |
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public static function inverseErrorCoefficients(int $termIndex): ImmutableFraction |
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{ |
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$terms =& static::$inverseErrorCoefs; |
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if (is_null(static::$inverseErrorCoefs)) { |
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$terms = new Vector(); |
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$terms->push(new ImmutableFraction(Numbers::makeOne(), Numbers::makeOne())); |
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$terms->push(new ImmutableFraction(Numbers::makeOne(), Numbers::makeOne())); |
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} |
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if ($terms->offsetExists($termIndex)) { |
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return $terms->get($termIndex); |
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} |
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$nextTerm = $terms->count(); |
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for ($k = $nextTerm;$k <= $termIndex;$k++) { |
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$termValue = new ImmutableFraction(new ImmutableDecimal('0'), new ImmutableDecimal('1')); |
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for ($m = 0;$m <= ($k - 1);$m++) { |
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$part1 = $terms->get($m); |
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$part2 = $terms->get($k - 1 - $m); |
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$part3 = $part1->multiply($part2); |
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$part4 = ($m + 1)*($m*2 + 1); |
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$part5 = $part3->divide($part4); |
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$termValue = $termValue->add($part5); |
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} |
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$termValue = $termValue->simplify(); |
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$terms->push($termValue); |
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} |
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return $terms->get($termIndex); |
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} |
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/** |
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* @param $z |
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* @param int $precision |
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* |
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* @return ImmutableDecimal |
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* @throws IntegrityConstraint |
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* @throws OptionalExit |
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* @throws \ReflectionException |
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*/ |
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public static function inverseGaussErrorFunction($z, int $precision = 10): ImmutableDecimal |
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{ |
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$z = Numbers::makeOrDont(Numbers::IMMUTABLE, $z); |
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$precision = $precision ?? $z->getPrecision(); |
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$internalPrecision = $precision + 1; |
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$pi = Numbers::makePi($internalPrecision); |
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$answer = SeriesProvider::maclaurinSeries( |
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$z, |
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function ($n) use ($pi) { |
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if ($n > 0) { |
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return $pi->pow($n)->multiply(StatsProvider::inverseErrorCoefficients($n)); |
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} |
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return Numbers::makeOne(); |
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}, |
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function ($n) { |
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return SequenceProvider::nthOddNumber($n); |
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}, |
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function ($n) { |
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if ($n > 0) { |
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$extra = Numbers::make(Numbers::IMMUTABLE, 2)->pow(SequenceProvider::nthEvenNumber($n)); |
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} else { |
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$extra = Numbers::makeOne(); |
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} |
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return SequenceProvider::nthOddNumber($n)->multiply($extra); |
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}, |
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0, |
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$internalPrecision |
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); |
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$answer = $answer->multiply($pi->sqrt($internalPrecision)->divide(2, $internalPrecision)); |
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return $answer->roundToPrecision($precision); |
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} |
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} |