diff --git a/Math/Functions/Functions.php b/Math/Functions/Functions.php
index 0af7c4755..88c4855a3 100755
--- a/Math/Functions/Functions.php
+++ b/Math/Functions/Functions.php
@@ -243,6 +243,73 @@ final class Functions
         return \abs(self::mod($value - $start, $length));
     }
 
+    private const ERF_COF = [
+        -1.3026537197817094, 6.4196979235649026e-1,
+        1.9476473204185836e-2,-9.561514786808631e-3,-9.46595344482036e-4,
+        3.66839497852761e-4,4.2523324806907e-5,-2.0278578112534e-5,
+        -1.624290004647e-6,1.303655835580e-6,1.5626441722e-8,-8.5238095915e-8,
+        6.529054439e-9,5.059343495e-9,-9.91364156e-10,-2.27365122e-10,
+        9.6467911e-11, 2.394038e-12,-6.886027e-12,8.94487e-13, 3.13092e-13,
+        -1.12708e-13,3.81e-16,7.106e-15,-1.523e-15,-9.4e-17,1.21e-16,-2.8e-17
+    ];
+
+    public static function getErf(float $x) : float
+    {
+        return $x > 0.0
+            ? 1.0 - self::erfccheb($x)
+            : self::erfccheb(-$x) - 1.0;
+	}
+
+    public static function getErfc(float $x) : float
+    {
+        return $x > 0.0
+            ? self::erfccheb($x)
+            : 2.0 - self::erfccheb(-$x);
+	}
+
+    private static function erfccheb(float $z) : float
+    {
+		$d = 0.;
+        $dd = 0.;
+
+        $ncof = \count(self::ERF_COF);
+
+		if ($z < 0.) {
+            throw new \InvalidArgumentException("erfccheb requires nonnegative argument");
+        }
+
+		$t = 2. / (2. + $z);
+		$ty = 4. * $t - 2.;
+
+		for ($j = $ncof - 1; $j > 0; --$j) {
+			$tmp = $d;
+			$d = $ty * $d - $dd + self::ERF_COF[$j];
+			$dd = $tmp;
+		}
+
+		return $t * \exp(-$z * $z + 0.5*(self::ERF_COF[0] + $ty * $d) - $dd);
+	}
+
+    public static function getInvErfc(float $p) : float
+    {
+		if ($p >= 2.0) {
+            return -100.;
+        } elseif ($p <= 0.0) {
+            return 100.;
+        }
+
+		$pp = ($p < 1.0) ? $p : 2. - $p;
+		$t = sqrt(-2. * \log($pp / 2.));
+		$x = -0.70711 * ((2.30753 + $t * 0.27061)/(1. + $t * (0.99229 + $t * 0.04481)) - $t);
+
+		for ($j = 0; $j < 2; ++$j) {
+			$err = self::getErfc($x) - $pp;
+			$x += $err / (1.12837916709551257 * \exp(-($x * $x)) - $x * $err);
+		}
+
+		return ($p < 1.0? $x : -$x);
+	}
+
     /**
      * Calculate the value of the error function (gauss error function)
      *
@@ -255,6 +322,7 @@ final class Functions
      *
      * @since 1.0.0
      */
+    /*
     public static function getErf(float $value) : float
     {
         if (\abs($value) > 2.2) {
@@ -280,6 +348,7 @@ final class Functions
 
         return 2 / \sqrt(\M_PI) * $sum;
     }
+    */
 
     /**
      * Calculate the value of the complementary error fanction
@@ -293,6 +362,7 @@ final class Functions
      *
      * @since 1.0.0
      */
+    /*
     public static function getErfc(float $value) : float
     {
         if (\abs($value) <= 2.2) {
@@ -323,6 +393,33 @@ final class Functions
 
         return 1 / \sqrt(\M_PI) * \exp(-$value * $value) * $q2;
     }
+    */
+
+    public static function getErfcInv(float $value) : float
+    {
+        if ($value >= 2) {
+            return \PHP_FLOAT_MIN;
+        } elseif ($value <= 0) {
+            return \PHP_FLOAT_MAX;
+        } elseif ($value === 1.0) {
+            return 0.0;
+        }
+
+        if ($ge = ($value >= 1)) {
+            $value = 2 - $value;
+        }
+
+        $t = \sqrt(-2 * \log($value / 2.0));
+        $x = -0.70711 * ((2.30753 + $t * 0.27061) / (1. + $t * (0.99229 + $t * 0.04481)) - $t);
+
+        $err = self::getErfc($x) - $value;
+        $x = $err / (1.12837916709551257 * \exp(-($x ** 2)) - $x * $err);
+
+        $err = self::getErfc($x) - $value;
+        $x = $err / (1.12837916709551257 * \exp(-($x ** 2)) - $x * $err);
+
+        return $ge ? -$x : $x;
+    }
 
     /**
      * Generalized hypergeometric function.