PHP实现简单线性回归之数据研究工具_web开发_PHP

 
var PiD2 = pi() / 2  

 
＜?php  

 // Distribution.php  

 // Copyright John Pezullo  
 // Released under same terms as PHP.  
 // PHP Port and OO'fying by Paul Meagher  

 class Distribution {  

  function doCommonMath($q, $i, $j, $b) {  
        
   $zz = 1;   
   $z  = $zz;   
   $k  = $i;   
        
        
   while($k ＜= $j) {   
        $zz = $zz * $q * $k / ($k - $b);   
        $z  = $z + $zz;   
        $k  = $k + 2;   
   }  
   return $z;  
  }  
        
  function getStudentT($t, $df) {    

   $t  = abs($t);   
   $w  = $t  / sqrt($df);   
   $th = atan($w);  
        
   if ($df == 1) {   
    return 1 - $th / (pi() / 2);   
   }  
      
   $sth = sin($th);   
   $cth = cos($th);  
      
   if( ($df % 2) ==1 ) {   
    return  
      1 - ($th + $sth * $cth * $this-＞doCommonMath($cth * $cth, 2, $df - 3, -1))  
                         / (pi()/2);  
   } else {  
    return 1 - $sth * $this-＞doCommonMath($cth * $cth, 1, $df - 3, -1);   
   }  
      
  }  
      
  function getInverseStudentT($p, $df) {   
        
   $v =  0.5;   
   $dv = 0.5;   
   $t  = 0;  
        
   while($dv ＞ 1e-6) {   
    $t = (1 / $v) - 1;   
    $dv = $dv / 2;   
    if ( $this-＞getStudentT($t, $df) ＞ $p) {   
     $v = $v - $dv;  
    } else {   
     $v = $v + $dv;  
    }   
   }  
   return $t;  
  }  
      

  function getFisherF($f, $n1, $n2) {  
   // implemented but not shown      
  }  

  function getInverseFisherF($p, $n1, $n2) {   
   // implemented but not shown      
  }  

 }  
 ?＞  

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